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|Pack date_time -- README.md|
The Date Time Library contains predicates that perform logical arithmetic on dates and times. It is an adapted version of the original
date_time library that is part of Amzi! Core Components by Amzi! inc., to be compatible with SWI-Prolog's module system.
date(Year,Month,Day) time(Hour,Minutes,Seconds) datetime(Year,Month,Day,Hour,Minutes,Seconds)
The various predicates try to do the correct thing when overflowing the various quantities, like taking into account the number of days in February when adding, say, 15 days to Feb 20th. The result will be a different day in March depending on whether the year is a leap year or not.
The predicates also recognize the last day of each month as a special case. So if you add a month to a date which is the last day of a month, you get the last day of the next month.
The structures represent absolute dates and times. Relative date/time quantities are represented by structures for each unit, with one argument which is the value. These structures are: years/1, months/1, weeks/1, days/1, hours/1, mins/1, and secs/1.
Each is defined as a postfix operator as well. So you can ask for example:
?- date_add(date(2002,1,15), 2 weeks, X). X = date(2002,1,29) yes
The library includes predicates to parse and create date and time strings.
This pack is available from the add-on registry of SWI-Prolog.
It can be installed with pack_install/1:
Then, you can use it by simply calling
Only for development purposes the
tap pack is needed:
date_get/2, % get a date for today, tomorrow, etc. date_create/4, % create a new date structure date_extract/2, % extract date fields from a date structure date_age/2, % compute an age from a birthday date_compare/3, % compare two dates date_add/3, % add years/months/weeks/days to a date date_difference/3, % find the difference between two dates date_interval/3, % find difference in single interval type (year, month, etc.) date_string/3, % convert between date structures and strings date_year_day/2, % calculate the day number for the year date_1900_days/2, % calculate the days since the 0th day of 1900 is_date_expression/1, % succeeds if expression is a special date expression is_date_interval/1, % succeeds if expression is a date interval is_date/1, % succeeds if expression is a date time_get/2, % gets the current time time_compare/3, % compares two times time_add/3, % add hours/mins/secs to a time time_difference/3, % find the difference between two times time_interval/3, % find the difference in single interval type(hour, min, sec) time_string/2, % convert between time structures and strings datetime_get/2, % get the current date and time datetime_compare/3, % compare two datetime structures datetime_add/3, % add datetime quantities to a datetime datetime_difference/3, % find the difference between two datetimes datetime_string/3, % convert to/from datetime strings datetime_date_time/3, % convert datetime to/from date and time structures datetime_extract/2, % extract years, months etc. from date time structure is_datetime_interval/1, % succeeds if expression is a date or time interval is_datetime/1, % succeeds if expression is a datetime week_dayn/2, % returns number for day of the week, 0 = Monday, 1 = Tuesday, ... week_day/2, % returns the day of the week for a date or datetime