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srfi-19

Time Data Types and Procedures

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Documentation

This is a Chicken port of SRFI 19. This document only describes the extensions. For the SRFI 19 API see SRFI 19.

Core Procedures

The core procedures are those pertaining to time, date, and timezone:

(require-extension srfi-19-core)

The core procedures can be separately accessed:

(require-extension srfi-19-time)
(require-extension srfi-19-date)
(require-extension srfi-19-timezone)
(require-extension srfi-19-io)

SRFI 19 Document Changes

The nanosecond time object element is an integer between 0 and 999,999,999 inclusive. (The SRFI 19 document mis-states the value.)

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.

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.

make-date
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.

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.

leap-year?
leap-year? DATEprocedure

Does the specified DATE fall on a leap year?

The DATE may be a numeric year or a date object.

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 => srfi-18#timeprocedure

Converts a SRFI 18 time object into a SRFI 19 time-duration object.

Time Conversion

seconds->time
(seconds->time SECONDS [TIME-TYPE time-duration]) => timeprocedure

Converts a SECONDS value, may be fractional, into a TIME-TYPE time object.

seconds->date
(seconds->date SECONDS [TIMEZONE-INFO #t]) => dateprocedure

Converts a SECONDS value, which may be fractional, into a date object. The TIMEZONE-INFO is #t for the local timezone, #f for the utc timezone, or a timezone-components object.

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

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 an inexact 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 an inexact seconds value.

time->date
time->date TIMEprocedure

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

time->julian-day
time->julian-day TIMEprocedure

Returns the julian day for the TIME object.

time->modified-julian-day
time->modified-julian-day TIMEprocedure

Returns the modified julian day for the TIME object.

Time Arithmetic

make-duration
(make-duration [#:days 0] [#:hours 0] [#:minutes 0] [#:seconds 0] [#:milliseconds 0] [#:microseconds 0] [#:nanoseconds 0]) => timeprocedure

Returns a time-object of clock-type time-duration where the seconds and nanoseconds values are calculated by summing the keyword arguments.

one-second-duration
one-second-durationprocedure
one-nanosecond-duration
one-nanosecond-durationprocedure
zero-time
(zero-time [TIME-TYPE time-duration]) => timeprocedure
TIME-FINE-GRAIN

Most minimum positive amount of time, as a duration.

divide-duration
divide-duration DURATION NUMBERprocedure

Returns a duration, from DURATION, divided by NUMBER, without remainder.

divide-duration!
divide-duration! DURATION NUMBERprocedure

Returns DURATION, divided by NUMBER, without remainder.

multiply-duration
multiply-duration DURATION NUMBERprocedure

Returns a duration, from DURATION, multiplied by NUMBER, truncated.

multiply-duration!
multiply-duration! DURATION NUMBERprocedure

Returns DURATION, multiplied by NUMBER, truncated.

time-negative?
time-negative? TIMEprocedure

Is TIME negative?

A time object will never have a negative nanoseconds value.

time-positve?
time-positve? TIMEprocedure

Is TIME positive?

time-zero?
time-zero? TIMEprocedure

Is TIME zero?

time-abs
time-abs TIMEprocedure

Returns the absolute time value, from TIME.

time-abs!
time-abs! TIMEprocedure

Returns the absolute TIME value.

time-negate
time-negate TIMEprocedure

Returns the sign inverted time value, from TIME.

time-negate!
time-negate! TIMEprocedure

Returns the TIME sign inverted value.

Time Comparison

time-compare
time-compare TIME1 TIME2procedure

Returns -1, 0, or 1.

time-max
time-max TIME1 #!optional TIME2...procedure

Returns the maximum time object from TIME1 TIME2....

time-min
time-min TIME1 #!optional TIME2...procedure

Returns the minimum time object from TIME1 TIME2....

Dates

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.

copy-date
copy-date DATEprocedure

Returns an exact copy of the specified DATE object.

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-zone-name
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 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 DATE-KEY #!optional CLOCK-TYPEprocedure

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

AMOUNT is an integer.

DATE-KEY is either 'years, 'quarters, 'months, 'days, 'hours, 'minutes, 'seconds, 'milliseconds, 'microseconds, or '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 DATE-KEY (ex: 'hours) follows the semantics of date-add-duration.

Date Comparison

date-compare
date-compare DATE1 DATE2procedure

Returns -1, 0, or 1.

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?

Timezone

Remember that SRFI 19 timezone offset follows ISO 8601.

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.

Probably 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.

Input/Output Procedures

(require-extension srfi-19-io)

DATE->STRING conversion specifiers

The SRFI 19 document does not mention the padding character override feature for the normally zero-padded conversions f, H, I, j, m, M, N, S, y. If the tilde is followed by a - then padding is suppressed. If followed by a _ the space character is used for padding. Otherwise zero-padding is perfomed, the default.

~[-_][fHIjmMNSy]

format-date
format-date DESTINATION DATE-FORMAT-STRING DATEprocedure

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

When the DESTINATION is #t the (current-output-port) is used, and the date object must be specified.

When the DESTINATION is a port it must be an output-port, and the date object must be specified.

When the DESTINATION is a number the (current-error-port) is the DESTINATION, and the DATE object must be specified.

When the DESTINATION is #f the result is returned as a string, and the DATE object must be specified.

format-date DATE-FORMAT-STRING DATEprocedure

Result is returned as a string.

scan-date
scan-date SOURCE TEMPLATE-STRINGprocedure

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

When the SOURCE is #t the (current-input-port) is used.

When the SOURCE is a port it must be an input-port.

When the SOURCE is string it should be a date text form.

Time Period

Usage

(require-extension srfi-19-period)

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

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.

copy-time-period
copy-time-period 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-length
time-period-length TIME-PERIODprocedure

Returns the time-duration of the TIME-PERIOD.

time-period-compare
time-period-compare TIME-PERIOD-1 TIME-PERIOD-2procedure

Returns -1 when TIME-PERIOD-1 < TIME-PERIOD-2, 0 when TIME-PERIOD-1 = TIME-PERIOD-2 and 1 TIME-PERIOD-1 > TIME-PERIOD-2.

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-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.

Usage

(require-extension srfi-19)

Notes

Requirements

locale srfi-29 miscmacros numbers check-errors record-variants

Bugs and Limitations

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.

Author

Kon Lovett

Version history

3.4.1
fix nanosecond squared value in date
3.4.0
add TIME-FINE-GRAIN, generalize make-time, add date-adjust.
3.3.6
Update leap second table.
3.3.5
3.3.4
Fix for ticket #630.
3.3.3
Fix for weekday name indexing, ticket #966.
3.3.2
Fix for removed ##sys#double->number.
3.3.1
Fix for time-monotonic->julian-day return, ticket #829.
3.3.0
Uses compiled setup-helper-mod.
3.2.0
Removed null time-period.
3.1.2
Fix for flonum (current-milliseconds). Fix for date-add/subtract-duration (actually time->date support for date-timezone-info). [Reported by Thomas Hintz]
3.1.1
Bug fix for non-unique month name key for May. Added padding character override information. The ZONE-OFFSET argument of make-date is optional. Added German bundle by Moritz Heidkamp.
3.1.0
Use of record-variants extension.
3.0.3
Bug fix for missing seconds->time & seconds->date in srfi-19. (Reported by Alex Suraci)
3.0.2
Bug fix for format-date output port check, format-date and scan-date argument type checks.
3.0.1
Bug fix for ~y input conversion.
3.0.0
Initial Chicken 4 release

License

Copyright (C) 2009-2017 Kon Lovett. All rights reserved.

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Copyright (C) I/NET, Inc. (2000, 2002, 2003). All Rights Reserved. Copyright (C) Neodesic Corporation (2000). All Rights Reserved.

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.

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