srfi-19

Time Data Types and Procedures

This is a Chicken port of SRFI-19. This document describes the original SRFI API (SRFI-19) and the extensions (*).

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srfi-19
- Abstract
- Specification
Documentation
SRFI 29 bundles
Examples
Notes
Bugs and Limitations
Requirements
Author
Repository
Acknowledgments
Version history
License

Points in time are represented as the number of seconds (with nanosecond precision) since "the epoch," a zero point in time. Several standard variants are defined, including UTC (universal coordinated time), TAI (international atomic time), and monotonic time. A point in time can also be represented as a Julian Day or Modified Julian Day number. Time durations, including time spent in a process or thread, are defined. Conversion routines are provided. The procedure CURRENT-TIME queries the current time in a specified variant, with a system-dependent resolution. Procedures for time arithmetic and time comparisons are also provided.

A date is a representation of a point in time in the Gregorian calendar, a 24 hour clock (with nanosecond precision) and a time zone offset from UTC. Procedures for converting between time and dates are provided, as well as for reading and writing string representations of dates.

Specification

A Time object, which is distinct from all existing types, defines a point in time or a time duration in some standard time system. The standard time systems are:

Universal Coordinated Time (UTC)
International Atomic Time (TAI)
monotonic time (a monotonically increasing point in time from Jan 1, 1970)
CPU time in current thread
CPU time in current process

Time duration.

A time object consists of three components:

Time type, a symbol representing the time system representation used. The constants time-tai, time-utc, time-monotonic, time-thread, time-process, and time-duration must be provided for these symbols.
Second, an integer representing the number of whole seconds from "the epoch."
Nanosecond, an integer of the number of nanoseconds in the fractional portion.

A Date object, which is distinct from all existing types, represents a point in time as represented by the Gregorian calendar as well as by a time zone. Dates are immutable. A date consists of the following components:

Nanosecond, an integer between 0 and 999,999,999, inclusive.
Second, an integer 0 and 60, inclusive, (60 represents a leap second)
Minute, an integer between 0 and 59, inclusive,
Hour, an integer between 0 and 23, inclusive,
Day, an integer between 0 and 31, inclusive, the upper limit depending on the month and year of the point in time,
Month, an integer between 1 and 12, inclusive; in which 1 means January, 2 February, and so on.
Year, an integer representing the year.
Time zone, an integer representing the number of seconds east of GMT for this timezone.

A Julian Day represents a point in time as a real number of days since -4713-11-24T12:00:00Z (midday UT on 24 November 4714 BC in the proleptic Gregorian calendar (1 January 4713 BC in the proleptic Julian calendar)).

A Modified Julian Day represents a point in time as a real number of days since 1858-11-17T00:00:00Z (midnight UT on 17 November AD 1858).

Timezone (*)

A tz-offset value follows ISO 8601; positive for east of UTC, and negative for west. This is the opposite of the POSIX TZ environment variable.

Where the SRFI-19 document states a tz-offset argument a timezone-components object is also legal; see Timezone

Documentation

Usage

Module srfi-19 reexports the time, date, timezone, literal, and io modules.

(import srfi-19)

Module srfi-19-core reexports the time, date, and timezone modules.

(import srfi-19-core)

Time

(import srfi-19-time)

Constants

time-duration

time-durationconstant: Symbol representing Time duration.

time-monotonic

time-monotonicconstant: Symbol representing monotonic time.

time-process

time-processconstant: Symbol representing time spent in current process.

time-tai

time-taiconstant: Symbol representing TAI time.

time-thread

time-threadconstant: Symbol representing time spent in current thread.

time-utc

time-utcconstant

Current time and clock resolution

current-time

current-time #!optional TIME-TYPEprocedure: Current time, of type time-type system, which defaults to TIME-UTC.

monotonic-time (*)

utc-time (*)

tai-time (*)

gc-time (*)

process-time (*)

thread-time (*)

(monotonic-time [SECS | NS SEC]) -> timeprocedure

(utc-time [SECS | NS SEC]) -> timeprocedure

(tai-time [SECS | NS SEC]) -> timeprocedure

(gc-time [SECS | NS SEC]) -> timeprocedure

(process-time [SECS | NS SEC]) -> timeprocedure

(thread-time [SECS | NS SEC]) -> timeprocedure

Returns like:

<none>: (current-time <time-type>).
SECS: (seconds->time SECS <time-type>).
NS SEC: (make-time <time-type> NS SEC).

From Chibi (srfi 19), with extensions.

time-resolution

time-resolution #!optional TIME-TYPEprocedure: Clock resolution, in nanoseconds, of the system clock of type type time-type system, which defaults to TIME-UTC.

Time object and accessors

make-time

make-time TYPE NANOSECOND SECONDprocedure: Creates a time object.

make-time* (*)

(make-time* [weeks: 0] [days: 0] [hours: 0] [minutes: 0] [seconds: 0] [milliseconds: 0] [microseconds: 0] [nanoseconds: 0] [time-type: duration]) -> timeprocedure: Returns a time-object of clock-type time-type where the seconds and nanoseconds values are calculated by summing the keyword arguments.

time?

time? OBJECTprocedure: #t if object is a time object, otherwise, #f.

time-type

time-type TIMEprocedure: Time type.

time-nanosecond

time-nanosecond TIMEprocedure: Time nanosecond.

time-second

time-second TIMEprocedure: Time second.

set-time-type!

set-time-type! TIME TIME-TYPEprocedure: Changes time type. Note: This changes the semantics of the time object. To convert a time to another system of representation, use one of the conversion procedures.

set-time-nanosecond!

set-time-nanosecond! TIME INTEGERprocedure: Changes time nanosecond.

set-time-second!

set-time-second! TIME INTEGERprocedure: Changes time second.

time-hash (*)

time-hash TIME #!optional BOUNDprocedure: Hash value for TIME within BOUND.

copy-time

time-copy (*)

copy-time TIMEprocedure
time-copy TIMEprocedure: Creates a new time, with the same time type, nanosecond, and second as TIME.

Time comparison procedures

All of the time comparison procedures require the time objects to be of the same type. It is an error to use these procedures on time objects of different types. For the point-in-time measurements (e.g., TIME-TAI and TIME-UTC), the semantics are described in plain text. For durations, (e.g., TIME-DURATION, TIME-CPU, the semantics are described in parentheses.

time-compare (*)

time-compare TIME1 TIME2procedure: Returns -1, 0, or +1.

time-min (*)

time-max (*)

time-min TIME1 #!optional TIME2...procedure
time-max TIME1 #!optional TIME2...procedure: Returns the minimum/maximum time object from TIME1 TIME2....

time<=?

time<=? TIME1 TIME2procedure: #t if time1 is before or at (less than or equal to) time2, #f otherwise.

time<?

time<? TIME1 TIME2procedure: #t if time1 is before (less than) time2, #f otherwise.

time=?

time=? TIME1 TIME2procedure: #t if time1 at (equal) time2, #f otherwise.

time>=?

time>=? TIME1 TIME2procedure: #t if time1 is at or after (greater than or equal to) time2, #f otherwise.

time>?

time>? TIME1 TIME2procedure: #t if time1 is after (greater than) time2, #f otherwise.

Time arithmetic procedures

Returns a 0 valued time of TIME-TYPE.

TIME-TYPE: (or time-tai time-utc time-monotonic time-thread time-process time-duration time-gc\)

time-difference

time-difference!

time-difference TIME1 TIME2procedure
time-difference! TIME1 TIME2procedure: The TIME-DURATION between time1 and time2. It is an error if time1 and time2 are of different time types.

add-duration

add-duration!

add-duration TIME1 TIME-DURATIONprocedure
add-duration! TIME1 TIME-DURATIONprocedure: The time resulting from adding time-duration to time1, which is a time object of the same time type as time1.

subtract-duration

subtract-duration!

subtract-duration TIME1 TIME-DURATIONprocedure
subtract-duration! TIME1 TIME-DURATIONprocedure: The time resulting from subtracting time-duration to time1, which is a time object of the same time type as time1.

divide-duration (*)

divide-duration! (*)

divide-duration DURATION REALprocedure
divide-duration! DURATION REALprocedure: Returns a duration, from DURATION, divided by REAL, without remainder.

multiply-duration (*)

multiply-duration! (*)

multiply-duration DURATION REALprocedure
multiply-duration! DURATION REALprocedure: Returns a duration, from DURATION, multiplied by REAL, truncated.

time-negative? (*)

time-positve? (*)

time-zero? (*)

time-negative? TIMEprocedure

time-positve? TIMEprocedure

time-zero? TIMEprocedure

Is TIME negative/positive/zero?

nonoseconds seconds where +/- - is negative, +/- + is positive, & 0 0 is zero.

time-abs (*)

time-abs! (*)

time-abs TIMEprocedure
time-abs! TIMEprocedure: Returns the absolute time value, from TIME.

time-negate (*)

time-negate! (*)

time-negate TIMEprocedure

time-negate! TIMEprocedure

Returns the sign inverted time value, from TIME.

Only time-second participates.

Time Conversion (*)

time->seconds

time->seconds TIMEprocedure: Returns the TIME object value as a seconds value; may be fractional.

seconds->time

(seconds->time SECONDS [TIME-TYPE time-duration]) -> timeprocedure: Converts a SECONDS value, may be fractional, into a TIME-TYPE time object.

time->nanoseconds

time->nanoseconds TIMEprocedure: Returns the TIME object value as a nanoseconds value.

nanoseconds->time

(nanoseconds->time NANOSECONDS [TIME-TYPE time-duration]) -> timeprocedure: Returns the NANOSECONDS value as a time TIME-TYPE object.

nanoseconds->seconds

nanoseconds->seconds NANOSECONDSprocedure: Returns the NANOSECONDS value as a seconds value.

time->milliseconds

time->milliseconds TIMEprocedure: Returns the TIME object value as a milliseconds value.

milliseconds->time

(milliseconds->time MILLISECONDS [TIME-TYPE time-duration]) -> timeprocedure: Returns the MILLISECONDS value as a time TIME-TYPE object.

milliseconds->seconds

milliseconds->seconds MILLISECONDSprocedure: Returns the MILLISECONDS value as a seconds value.

SRFI-18 Time (*)

Note that the SRFI-18 identifiers time?, current-time, seconds->time, time->seconds, milliseconds->time, and time->milliseconds are in conflict with those of SRFI-19.

time->srfi-18-time

time->srfi-18-time TIMEprocedure: Converts a SRFI-19 time object to a SRFI-18 time object. The conversion is really only meaningful for time-duration, but any time-type is accepted.

srfi-18-time->time

srfi-18-time->time TIMEprocedure: Converts a SRFI-18 time object into a SRFI-19 time-duration object.

Date

(import srfi-19-date)

Types

TIMEZONE-INFO is a tz-offset, a boolean where #t is (local-timezone-locale) & #f is (utc-timezone-locale), or a timezone-components.

Current date

current-date

current-date #!optional TZ-OFFSETprocedure: Date corresponding to the current UTC time.

current-julian-day

current-julian-dayprocedure: Current Julian Day.

current-modified-julian-day

current-modified-julian-dayprocedure: Current Modified Julian Day.

Date object and accessors

Date objects are immutable once created.

default-date-clock-type

(default-date-clock-type [CLOCK-TYPE time-utc]) -> symbolparameter: Sets or gets the clock-type used by default for conversion of a date to a time.

make-date (extended)

make-date NANOSECOND SECOND MINUTE HOUR DAY MONTH YEAR #!optional ZONE-OFFSET TZ-NAME DST-FLAGprocedure

Same as SRFI-19 except for the optional parameters and allowing a timezone-components object for the ZONE-OFFSET.

The ZONE-OFFSET is an integer or timezone-components. Default is the (timezone-locale-offset), the current locale timezone offset.

The TZ-NAME is a string or #f, and is the timezone name. Default is #f.

The DST-FLAG is a boolean, and indicates whether Day Saving TIme (or Summer Time) is active. Default is #f.

When the ZONE-OFFSET is a timezone-components object the TZ-NAME and DST-FLAG are pulled from the timezone-components, unless explicitly supplied.

copy-date (*)

date-copy (*)

copy-date DATEprocedure
date-copy DATEprocedure: Returns an exact copy of the specified DATE object.

date?

date? DATEprocedure: #t if object is a time object, otherwise, #f.

date-nanosecond

date-nanosecond DATEprocedure: Date nanosecond.

date-second

date-second DATEprocedure: Date second.

date-minute

date-minute DATEprocedure: Date minute.

date-hour

date-hour DATEprocedure: Date hour.

date-day

date-day DATEprocedure: Date day.

date-month

date-month DATEprocedure: Date month.

date-year

date-year DATEprocedure: Date year.

date-zone-offset

date-zone-offset DATEprocedure: Date time zone offset.

date-zone-name (*)

date-zone-name DATEprocedure
date-zone-name DATEprocedure: Returns the timezone abbreviation of the specified DATE object. The result is either a string or #f.

date-dst? (*)

date-dst? DATEprocedure

Returns the daylight saving time flag of the specified DATE object.

Only valid for "current" dates. Historical dates will not have a correct setting. Future dates cannot have a correct setting.

date-year-day

date-year-day DATEprocedure: The ordinal day of the year of this date. January 1 is 1, etc.

date-week-day

date-week-day DATEprocedure: The day of the week of this date, where Sunday=0, Monday=1, etc.

date-week-number

date-week-number DATE DAY-OF-WEEK-STARTING-WEEKprocedure: The ordinal week of the year which holds this date, ignoring a first partial week. 'Day-of-week-starting-week' is the integer corresponding to the day of the week which is to be considered the first day of the week (Sunday=0, Monday=1, etc.).

leap-year? (*)

leap-year? YEARprocedure

Is the specified YEAR a leap year?

YEAR: (or fixnum date) ; numeric year or date object.

leap-day? (*)

leap-day? DATEprocedure

Is the specified DATE a leap day?

The leap day of the leap month of a leap year.

Time/Date/Julian Day/Modified Julian Day Converters

seconds->date

(seconds->date SECONDS [TZ-OFFSET #t]) -> dateprocedure

Converts a SECONDS value, which may be fractional, into a date object.

SECONDS is relative to 00:00:00 January 1, 1970 UTC.

date->seconds (*)

date->seconds DATE #!optional CLOCK-TYPE default-date-clock-typeprocedure

Returns the specified DATE as as a seconds value, based on the CLOCK-TYPE.

The seconds value is relative to the TAI-EPOCH - 1 January 1970 CE at 00:00:00 UTC.

time->date

time->date TIMEprocedure: Returns the TIME object value as a date. A shorthand for the (time-*->date...) procedures.

date->time (*)

date->time DATE #!optional CLOCK-TYPE default-date-clock-typeprocedure: Returns the specified DATE as a time-object of type CLOCK-TYPE.

date->julian-day

date->julian-day DATEprocedure: Convert date to Julian Day.

date->modified-julian-day

date->modified-julian-day DATEprocedure: Convert date to Modified Julian Day.

date->time-monotonic

date->time-monotonic DATEprocedure: Convert date to monotonic time.

date->time-tai

date->time-tai DATEprocedure: Convert date to TAI time.

date->time-utc

date->time-utc DATEprocedure: Convert date to UTC time.

time->julian-day

time->julian-day TIMEprocedure: Returns the julian day for the TIME object.

julian-day->date

julian-day->date JD #!optional TZ-OFFSETprocedure: Convert Julian Day to date, , using time zone offset, which defaults to the local time zone.

julian-day->time-monotonic

julian-day->time-monotonic JDprocedure: Convert Julian Day to monotonic time.

julian-day->time-tai

julian-day->time-tai JDprocedure: Convert Julian Day to TAI time.

julian-day->time-utc

julian-day->time-utc JDprocedure: Convert Julian Day to UTC time.

time->modified-julian-day

time->modified-julian-day TIMEprocedure: Returns the modified julian day for the TIME object.

modified-julian-day->date

modified-julian-day->date MJD #!optional TZ-OFFSETprocedure: Convert Modified Julian Day to date, using time zone offset, which defaults to the local time zone.

modified-julian-day->time-monotonic

modified-julian-day->time-monotonic MJDprocedure: Convert Modified Julian Day to monotonic time.

modified-julian-day->time-tai

modified-julian-day->time-tai MJDprocedure: Convert Modified Julian Day to TAI time.

modified-julian-day->time-utc

modified-julian-day->time-utc MJDprocedure: Convert Modified Julian Day to UTC time.

time-monotonic->date

time-monotonic->date TIME-MONOTONIC #!optional TZ-OFFSETprocedure: Convert monotonic time to date, using time zone offset, which defaults to the local time zone.

time-monotonic->julian-day

time-monotonic->julian-day TIME-MONOTONICprocedure: Convert monotonic time to Julian Day.

time-monotonic->modified-julian-day

time-monotonic->modified-julian-day TIME-MONOTONICprocedure: Convert monotonic time to Modified Julian Day.

time-monotonic->time-tai

time-monotonic->time-tai TIME-MONOTONICprocedure: Convert monotonic time to TAI time.

time-monotonic->time-tai!

time-monotonic->time-tai! TIME-MONOTONICprocedure: Convert monotonic time to TAI time. The time structure may be reused.

time-monotonic->time-utc

time-monotonic->time-utc TIME-MONOTONICprocedure: Convert monotonic time to UTC time.

time-monotonic->time-utc!

time-monotonic->time-utc! TIME-MONOTONICprocedure: Convert monotonic time to UTC time. The time structure may be reused.

time-tai->date

time-tai->date TIME-TAI #!optional TZ-OFFSETprocedure: Convert TAI time to date, using time zone offset, which defaults to the local time zone.

time-tai->julian-day

time-tai->julian-day TIME-TAIprocedure: Convert TAI time to Julian Day.

time-tai->modified-julian-day

time-tai->modified-julian-day TIME-TAIprocedure: Convert TAI time to Modified Julian Day.

time-tai->time-monotonic

time-tai->time-monotonic TIME-TAIprocedure: Convert TAI time to monotonic time.

time-tai->time-monotonic!

time-tai->time-monotonic! TIME-TAIprocedure: Convert TAI time to monotonic time. The time structure may be reused.

time-tai->time-utc

time-tai->time-utc TIME-TAIprocedure: Convert TAI time to monotonic time.

time-tai->time-utc!

time-tai->time-utc! TIME-TAIprocedure: Convert TAI time to monotonic time. The time structure may be reused.

time-utc->date

time-utc->date TIME-UTC #!optional TZ-OFFSETprocedure: Convert UTC time to date, using time zone offset, which defaults to the local time zone.

time-utc->julian-day

time-utc->julian-day TIME-UTCprocedure: Convert UTC time to Julian Day

time-utc->modified-julian-day

time-utc->modified-julian-day TIME-UTCprocedure: Convert UTC time to Modified Julian Day.

time-utc->time-monotonic

time-utc->time-monotonic TIME-UTCprocedure: Convert UTC time to monotonic time.

time-utc->time-monotonic!

time-utc->time-monotonic! TIME-UTCprocedure: Convert UTC time to monotonic time. The time structure may be reused.

time-utc->time-tai

time-utc->time-tai TIME-UTCprocedure: Convert UTC time to TAI time.

time-utc->time-tai!

time-utc->time-tai! TIME-UTCprocedure: Convert UTC time to TAI time. The time structure may be reused.

Date Arithmetic (*)

date-difference

date-difference DATE1 DATE2 #!optional CLOCK-TYPEprocedure: Returns the time-duration between DATE1 and DATE2.

date-add-duration

date-add-duration DATE DURATION #!optional CLOCK-TYPEprocedure: Returns a new date, the DATE plus the DURATION.

date-subtract-duration

date-subtract-duration DATE DURATION #!optional CLOCK-TYPEprocedure: Returns a new date, the DATE minus the DURATION.

date-adjust

date-adjust DATE AMOUNT KEY #!optional CLOCK-TYPEprocedure

Returns a new date, the DATE adjusted by the AMOUNT of KEY.

AMOUNT: integer ;
KEY: symbol ; '(years quarters months weeks days hours minutes seconds milliseconds microseconds nanoseconds).

If the day of the month of DATE is greater than the number of days in the final month, the day of the month will change to the last day in the final month.

Adjusting a time KEY (ex: 'hours) follows the semantics of date-add-duration.

date-adjust*

date-adjust* DATE KEY AMOUNT ... #!optional CLOCK-TYPEprocedure

Returns a new date, the DATE adjusted by each of the KEY AMOUNT pairs, in-order.

AMOUNT: integer ;
KEY: keyword ; '(years: quarters: months: weeks: days: hours: minutes: seconds: milliseconds: microseconds: nanoseconds).:

A convenience wrapper of date-adjust.

Date Comparison (*)

date-compare

date-compare DATE1 DATE2procedure: Returns -1, 0, or +1.

date-hash

date-hash DATE #!optional BOUNDprocedure: Hash value for DATE within BOUND.

date=?

date=? DATE1 DATE2procedure: Is DATE1 on DATE2?

date>?

date>? DATE1 DATE2procedure: Is DATE1 after DATE2?

date<?

date<? DATE1 DATE2procedure: Is DATE1 before DATE2?

date>=?

date>=? DATE1 DATE2procedure: Is DATE1 after or on DATE2?

date<=?

date<=? DATE1 DATE2procedure: Is DATE1 before or on DATE2?

read-leap-second-table

read-leap-second-table FILENAMEprocedure

Sets the leap second table from the specified FILENAME.

The file format is the same as the "tai-utc.dat" file in the distribution. Provided by the U.S. Naval Observatory.

Timezone (*)

The daylight saving time (summer time) flag is always taken from the system (locale egg) unless supplied. Any summer time rule component of a timezone-components object is not processed.

TZ-COMPONENTS: timezone-components ;a timezone object

SRFI-19 timezone offset follows ISO 8601; positive for east of UTC, and negative for west. This is the opposite of the POSIX TZ environment variable.

(import srfi-19-timezone)

local-timezone-locale

local-timezone-locale #!optional TZ-COMPONENTSparameter: Gets or sets the local timezone-locale object.

utc-timezone-locale

utc-timezone-locale #!optional TZ-COMPONENTSparameter

Gets or sets the utc timezone-locale object.

Not a good idea to change the value.

timezone-locale-name

timezone-locale-name #!optional TZ-COMPONENTSprocedure: Returns the timezone-locale name of the supplied TZ-COMPONENTS, or the (local-timezone-locale) if missing.

timezone-locale-offset

timezone-locale-offset #!optional TZ-COMPONENTSprocedure: Returns the timezone-locale offset of the supplied TZ-COMPONENTS, or the (local-timezone-locale) if missing.

timezone-locale-dst?

timezone-locale-dst? #!optional TZ-COMPONENTSprocedure: Returns the timezone-locale daylight saving time flag of the supplied TZ-COMPONENTS, or the (local-timezone-locale) if missing.

Date to String/String to Date Converters (Input/Output Procedures)

(import srfi-19-io)

format-date (*)

format-date DESTINATION DATE-FORMAT DATEprocedure

format-date DATE-FORMAT DATEprocedure

Displays a text form of the DATE on the DESTINATION using the DATE-FORMAT.

DESTINATION: ; the result is returned as a string.
DESTINATION: #f ; the result is returned as a string.
DESTINATION: #t ; the (current-output-port) is used.
DESTINATION: output-port ; text output port.
DESTINATION: number ; the (current-error-port) is the DESTINATION.

scan-date (*)

scan-date SOURCE TEMPLATEprocedure

Reads a text form of a date from the SOURCE, following the TEMPLATE, and returns a date object.

SOURCE: #t ; (current-input-port).
SOURCE: input-port ; text input port.
SOURCE: string ; a date text form.

A partial date resulting from a time-only format, missing the d-m-y, is completed with from the (current-date), as is any timezone information, and missing h:m:s:ns are 0.

date->string

date->string DATE #!optional DATE-FORMATprocedure

DATE: date
DATE-FORMAT: string ; default "~c".

string->date

string->date SOURCE #!optional TEMPLATEprocedure

SOURCE: see scan-date.
TEMPLATE: string ; default (localized-template/default 'srfi-19 'date-time).

The string->date procedure allows the template-name argument to be optional. When missing the locale's date-time-format string is used. The supplied locale bundle's strings are invertible.

DATE->STRING conversion specifiers

Conversion specifier form : ~[-_][fHIjmMNSy]

Ch	Conversion
~~	a literal ~
~a	locale's abbreviated weekday name (Sun...Sat)
~A	locale's full weekday name (Sunday...Saturday)
~b	locale's abbreviate month name (Jan...Dec)
~B	locale's full month day (January...December)
~c	locale's date and time (e.g., "Fri Jul 14 20:28:42-0400 2000")
~d	day of month, zero padded (01...31)
~D	date (mm/dd/yy)
~e	day of month, blank padded ( 1...31)
~f	seconds+fractional seconds, using locale's decimal separator (e.g. 5.2).
~g	day of month
~h	same as ~b
~H	hour, zero padded, 24-hour clock (00...23)
~I	hour, zero padded, 12-hour clock (01...12)
~j	day of year, zero padded
~k	hour, blank padded, 24-hour clock ( 0...23)
~l	hour, blank padded, 12-hour clock ( 1...12)
~m	month, zero padded (01...12)
~M	minute, zero padded (00...59)
~n	new line
~N	nanosecond, zero padded
~p	locale's AM or PM
~r	time, 12 hour clock, same as "~I:~M:~S ~p"
~s	number of full seconds since "the epoch" (in UTC)
~S	second, zero padded (00...60)
~t	horizontal tab
~T	time, 24 hour clock, same as "~H:~M:~S"
~u	day ordinal suffix
~U	week number of year with Sunday as first day of week (00...53)
~V	ISO 8601 week number of the year with Monday as first day of week (01..53)
~w	day of week (0...6)
~W	week number of year with Monday as first day of week (01...52)
~x	locale's date representation
~X	locale's time representation
~y	last two digits of year (00...99)
~Y	4-digit year
~z	time zone in RFC-822 style
~Z	symbol time zone (not-implemented)
~1	ISO-8601 year-month-day format
~2	ISO-8601 hour-minute-second-timezone format
~3	ISO-8601 hour-minute-second format
~4	ISO-8601 year-month-day-hour-minute-second-timezone format
~5	ISO-8601 year-month-day-hour-minute-second format

The normally zero-padded conversions f, H, I, j, m, M, N, S, y have a padding character override feature. If the tilde is followed by a - then padding is suppressed. If followed by a _ the space character is used for padding. Otherwise, the default, zero-padding is perfomed.

g - day of month. It just outputs the day of the month (1...31). The other two standard directives both specify either blank padding or zero padding but there's no option for no padding.
u - day ordinal suffix. Outputs the locale-specific suffix for the day of the month. For example "rd" for 3, "th" for 6, or "st" for 21. This allows you to format dates as "Sunday, 1st of January 2017". It's possible to insert the "st" in such a format string manually but it doesn't seem a clean approach.

g & u from Chibi (srfi 19).

STRING->DATE conversion specifiers

Ch	Skip to	Read	Set
~~	any	read literal	~
~a	char-alphabetic?	abbreviated weekday in locale	nothing
~A	char-alphabetic?	full weekday in locale	nothing
~b	char-alphabetic?	abbreviated month name in locale	nothing
~B	char-alphabetic?	full month name in locale	nothing
~d	char-numeric?	day of month	date-day
~e	any	day of month, blank padded	date-day
~f	char-decimal?	seconds+fractional seconds, using locale's decimal separator (e.g. 5.2).	date-second+date-nanosecond
~h	char-alphabetic?	same as ~b	nothing
~H	char-numeric?	hour	date-hour
~k	any	hour, blank padded	date-hour
~m	char-numeric?	month	date-month
~M	char-numeric?	minute	date-minute
~S	char-numeric?	second	date-second
~y	any	2-digit year	date-year within 50 years
~Y	char-signed-numeric?	4-digit year	date-year
~z	any	time zone	date-zone-offset

Date/Time Literals (*)

Literal Date/Time forms.

Usage

(import srfi-19-literals)

date-literal-form

date-literal-form #!optional FORMparameter

The date literal format.

#f: #<srfi-19#date ...>
SRFI-10: #,(srfi-19-date ...)
#t: #@... ; the default
|#@|: #@...

time-literal-form

time-literal-form #!optional FORMparameter

The time literal format.

#f: #<srfi-19#time ...>
SRFI-10: #,(srfi-19-time ...) ; the default
#t ##...
|##|: ##...

Use the ## form at your peril.

read-date-literal

read-date-literal #!optional PORTprocedure

Read a date-literal from the PORT, in one of the supported forms, and return the object creation source form; '(make-date ....).

PORT: input-port ; default (current-input-port)

Supported forms:

"~Y-~m-~dT~H:~M:~f~z": date time timezone
"~Y-~m-~dT~H:~M:~f": date time
"~Y-~m-~d": date
"~H:~M:~f~z": time timezone; date components from (current-date)
"~H:~M:~f": time; date components from (current-date)

write-date-literal

write-date-literal DATE #!optional PORTprocedure

Write the DATE to the PORT using a string ISO form; "~Y-~m-~dT~H:~M:~f~z".

PORT: output-port ; default (current-output-port)

Time Period (*)

A time-period is an interval, [begin end), where begin and end are time objects of the same clock type.

Usage

(import srfi-19-period)

make-time-period

make-time-period BEGIN END #!optional CLOCK-TYPE default-date-clock-typeprocedure

Returns a new time-period object. The clock types must be compatible.

BEGIN maybe a seconds value, a date, or a time (except time-duration). A seconds value or date are converted to CLOCK-TYPE.

END maybe a seconds value, a date, or a time. A seconds value or date are converted to the same clock type as BEGIN. A time-duration is treated as an offset from BEGIN.

time-period-copy

time-period-copy TIME-PERIODprocedure: Returns a copy of TIME-PERIOD.

time-period-begin

time-period-begin TIME-PERIODprocedure: Returns the start time for the TIME-PERIOD.

time-period-end

time-period-end TIME-PERIODprocedure: Returns the end time for the TIME-PERIOD.

time-period-last

time-period-last TIME-PERIODprocedure: Returns the last time for the TIME-PERIOD; (time-period-end - TIME-FINE-GRAIN).

time-period-type

time-period-type TIME-PERIODprocedure: Returns the clock-type of the TIME-PERIOD.

time-period?

time-period? OBJECTprocedure: Is OBJECT a time-period?

time-period-duration

time-period-duration TIME-PERIODprocedure: Returns the time-duration of the TIME-PERIOD.

time-period-hash

time-period-hash TIME-PERIOD #!optional BOUNDprocedure: Hash value for TIME-PERIOD within BOUND.

time-period-compare

time-period-compare TIME-PERIOD-1 TIME-PERIOD-2procedure: Returns -1, 0, or +1.

time-period=?

time-period=? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 begin & end with TIME-PERIOD-2?

time-period<?

time-period<? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 end before TIME-PERIOD-2 begins?

time-period>?

time-period>? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 begin after TIME-PERIOD-2 ends?

time-period<=?

time-period<=? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 end on or before TIME-PERIOD-2 begins?

time-period>=?

time-period>=? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 begin on or after TIME-PERIOD-2 ends?

time-period-precedes?

time-period-meets?

time-period-overlaps?

time-period-finished-by?

time-period-contains?

time-period-starts?

time-period-equals?

time-period-started-by?

time-period-during?

time-period-finishes?

time-period-overlapped-by?

time-period-met-by?

time-period-preceded-by?

time-period-precedes? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-meets? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-overlaps? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-finished-by? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-contains? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-starts? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-equals? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-started-by? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-during? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-finishes? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-overlapped-by? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-met-by? TIME-PERIOD-1 TIME-PERIOD-2procedure
time-period-preceded-by? TIME-PERIOD-1 TIME-PERIOD-2procedure: Returns the relationship per Allen's Interval Algebra.

time-period-preceding

time-period-preceding TIME-PERIOD-1 TIME-PERIOD-2procedure: Return the portion of TIME-PERIOD-1 before TIME-PERIOD-2 or #f when it doesn't precede.

time-period-succeeding

time-period-succeeding TIME-PERIOD-1 TIME-PERIOD-2procedure: Return the portion of TIME-PERIOD-1 after TIME-PERIOD-2 or #f when it doesn't succeed.

time-period-contains/period?

time-period-contains/period? TIME-PERIOD-1 TIME-PERIOD-2procedure: Is TIME-PERIOD-2 within TIME-PERIOD-1?

time-period-contains/time?

time-period-contains/time? TIME-PERIOD TIMEprocedure

Is TIME within TIME-PERIOD?

TIME is converted to a compatible clock-type if possible.

time-period-contains/date?

time-period-contains/date? TIME-PERIOD DATEprocedure

Is DATE within TIME-PERIOD?

DATE is converted to a compatible time if possible.

time-period-contains?

time-period-contains? TIME-PERIOD OBJECTprocedure

Is OBJECT within TIME-PERIOD?

OBJECT maybe a time, date, or time-period.

time-period-intersects?

time-period-intersects? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-2 overlap TIME-PERIOD-1?

time-period-intersection

time-period-intersection TIME-PERIOD-1 TIME-PERIOD-2procedure: The overlapping time-period of TIME-PERIOD-2 and TIME-PERIOD-1, or #f when no overlap.

time-period-union

time-period-union TIME-PERIOD-1 TIME-PERIOD-2procedure: Returns the time-period spanned by TIME-PERIOD-1 and TIME-PERIOD-2, or #f when they do not intersect.

time-period-span

time-period-span TIME-PERIOD-1 TIME-PERIOD-2procedure: Returns the time-period spanned by TIME-PERIOD-1 and TIME-PERIOD-2, including any gaps.

time-period-shift

time-period-shift TIME-PERIOD DURATIONprocedure: Returns a copy of TIME-PERIOD shifted by DURATION.

time-period-shift!

time-period-shift! TIME-PERIOD DURATIONprocedure: Returns TIME-PERIOD shifted by DURATION.

SRFI 29 bundles

Installed w/ the egg are:

en: English (American) - only shipping u support at the moment
de: German
it: Italian
es: Spanish
nl: Dutch
pt_br: Brazilian Portuguese

Default bundle is en.

Examples

Prevent default timezone initialization by explicitly setting the 'timezone.

;must be done before 1st invocation of a srfi-19 export
(import locale)
(set-locale-category! 'timezone
  (posix-timezone-string->timezone-components
    ;some acceptable posix tz form
    "XSX+2:00XDX+1:00:00"
    ;source of tz info
    '("POSIX" "TZ")))

(current-timezone-components)
;=> ((tag . timezone) (name . "XSX+2:00XDX+1:00:00") (source "POSIX" "TZ")
;=> (std-name . "XSX") (std-offset . 7200) (dst-name . "XDX") (dst-offset . 3600)
;=> (dst? . #t))

;now we can use srfi-19 in our runtime tz
(import (chicken format))
(import srfi-19)
(format #t "Present Day: ~A~%Present Time: ~A~%: Hah, hah, hah.~%"
  (current-date) (current-time))

Provide SRFI-128 comparators.

(import (only (srfi 128) make-comparator))

(define (make-date-comparator)
  (import (only srfi-19-date date? date=? date<? date-hash))
  (make-comparator date? date=? date<? date-hash) )

(define (make-time-comparator)
  (import (only srfi-19-time time? time=? time<? time-hash))
  (make-comparator time? time=? time<? time-hash) )

(define (make-time-period-comparator)
  (import (only srfi-19-period time-period? time-period=? time-period<? time-period-hash))
  (make-comparator srfi-19-period time-period? time-period=? time-period<? time-period-hash) )

Notes

The string->date and scan-date procedures will not create an incomplete date. At a minimum the input must include day, month and year or hour, minute, second; the time and timezone default to 0 and the locale, respectively.
Year 0 is supported per ISO 8601 & XML Date.
The SRFI-18 current-time and time? bindings conflict with SRFI-19 bindings.
A SRFI-18 time object is not accepted except by the conversion procedures.
The English (en) SRFI 29 bundle is American.

Bugs and Limitations

Local timezone information is not valid for historic dates and problematic for future dates. Daylight saving time is especially an issue. Conversion of a time or seconds value to a local date will use the current timezone offset value. The current offset will reflect the daylight saving time status. So target dates outside of the DST period will be converted incorrectly!
Will only read years in the range -9999..9999 properly. The ISO 8601 year convention for years 10000 CE and after is not supported.
Cannot swap SRFI 29 bundle. Fixed at load time.
Using date-adjust for the same date-key MomentJS says:

If you are adding hours, minutes, seconds, or milliseconds, the assumption is that you want precision to the hour, and will result in a different hour.

var m = moment(new Date(2011, 2, 12, 5, 0, 0)); // the day before DST in the US
m.hours(); // 5
m.add(24, 'hours').hours(); // 6

but this implementation says 1 day = 24 hours, so same hour.

The omnibus modules, srf-19-core & srf-19, do not have accurate type or lambda-info. Use the component modules.
See SRFI 29 bundles for u conversion support.

Requirements

utf8 srfi-1 srfi-18 srfi-29 miscmacros locale record-variants check-errors

Test Only

Test test-utils format

Author

Kon Lovett

Repository

This egg is hosted on the CHICKEN Subversion repository:

https://anonymous@code.call-cc.org/svn/chicken-eggs/release/5/srfi-19

If you want to check out the source code repository of this egg and you are not familiar with Subversion, see this page.

Acknowledgments

Special thanks for the German (de), Italian (it), Spanish (es), Dutch (nl), and Brazilian Portuguese (pt_br) SRFI 29 bundles.
The date-literal is copied from the CHICKEN 4 egg date-literals by Arto Bendiken.

Version history

4.10.2: Fix seconds->date optional timezone-info.
4.10.1: Fix signatures (again).
4.10.0: Extend <time-type>-time functions. Fix signatures.
4.9.11: Remove useless signatures (bug reported by shawnw on #chicken irc).
4.9.10: Add make-time*, deprecate make-duration, fix signatures.
4.9.9: Read BCE (full) years (~Y).
4.9.8: Fix parameters error on bad argument.
4.9.7: Add ~f input conversion. Fix time-period-compare.
4.9.6: Register the feature. Add leap-day?.
4.9.5: Remove code/data duplicates.
4.9.4: Restore copy-time & add copy-date.
4.9.3: Fix *-hash range test.
4.9.2: Fix time-hash result bounds.
4.9.1: Fix date-adjust synonym lookup.
4.9.0: SRFI-69 conforming date-hash, time-hash, & period-hash. Drop srfi-69 dependency.
4.8.2: Fix ~V.
4.8.1: Better date/time-hash. Fix time-compare negative seconds. nanoseconds->time, milliseconds->time, seconds->time, & date->seconds have optional. time-abs & time-negate affect time-second only.
4.8.0: Add Chibi time routines. Fix seconds->time & time->seconds negative seconds.
4.7.5: Add default locale bundle.
4.7.4: Add C locale bundle.
4.7.3: make-date accepts year 0.
4.7.2: date-adjust* accepts symbols.
4.7.1: Fix date<?/date>? swapped bug; reported on #irc by gahr, Jan 26 '23
4.7.0: Add Chibi ~g & ~u output conversion specifiers.
4.6.0: Add date-adjust*.
4.5.2: Better time-literal-form default.
4.5.1: Fix SRFI-69 compatible time-hash, date-hash, time-period-hash.
4.5.0: Add SRFI-69/128 compatible time-hash, date-hash, time-period-hash.
4.4.10: Indicate pure procedures. Fix time conversion procedure signatures.
4.4.9: Add strong typing.
4.4.8: Fix time-copy, add time-copy/date-copy, deprecate copy-date && copy-time, add time-period interval relations.
4.4.7: .
4.4.6: Fix time-utc->date default TZ.
4.4.0: Add Date/Time source literals via the srfi-19-literals module.
4.3.2: Allow partial (time only) date read.
4.3.1: .
4.3.0: Deprecate 'srfi-10 record print form. Fix record printing.
4.3.0: nanoseconds->seconds, milliseconds->seconds, & date->seconds do not necessarily return an inexact.
4.2.1: .
4.2.0: Fix make-date w/o tz.
4.1.2: .
4.1.1: Fix seconds->date flonum argument handling.
4.1.0: Variants.
4.0.2: Add dependencies.
4.0.1: Add dependencies.
4.0.0: C5 port.

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the Software), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ASIS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Scheme Request For Implementation process or editors, except as needed for the purpose of developing SRFIs in which case the procedures for copyrights defined in the SRFI process must be followed, or as required to translate it into languages other than English.

The limited permissions granted above are perpetual and will not be revoked by the authors or their successors or assigns.

This document and the information contained herein is provided on an "AS IS" basis and THE AUTHOR AND THE SRFI EDITORS DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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