An ASP Library for dates

• Dates are represented as tuple terms (D,M,Y).
• Library converts absolute dates into relative dates.
• Library finds out the weekday of a date.
• Library can create date tuples for every day in a given month or year.
• Day differences are realized using Julian Day Numbers, see http://quasar.as.utexas.edu/BillInfo/JulianDatesG.html .
• Week days are realized using a formula from https://de.wikipedia.org/wiki/Wochentagsberechnung

Input Predicates

date_consider_month/2( M, Y )

Creates all dates of the given month in the given year that need to be considered.

Argument	Domain	Note
M	number (1-12)	Month
Y	number (1XXX-2XXX)	Year

date_consider_year/2( Y )

Creates all dates of the given year that need to be considered.

Argument	Domain	Note
Y	number (1XXX-2XXX)	Year

date_origin/1( (D,M,Y) )

Define the origin date for relative date computations.

Arguments are as with date_consider/1.

Output Predicates

date_consider/1( (D,M,Y) )

Dates that will be considered. Do NOT use it to create dates! It allows the creation of illegal dates i.e. 29th of February on a non leap year.

Argument	Domain	Note
D	number (1-31)	Day of Month
M	number (1-12)	Month
Y	number (1XXX-2XXX)	Year

date_julian/2( (D,M,Y), JulianDay )

Mapping from considered dates to Julian Day number (number of days since 1st of January -4712).

Remark: the "half day" of Julian Day computation is omitted. This preserves correctness of relative day counts.

Argument	Domain	Note
D	number (1-31)	Day of Month
M	number (1-12)	Month
Y	number (1XXX-2XXX)	Year
JulianDay	positive number	Number of Days since 1st of January -4712

date_relative/2( (D,M,Y), Days )

Mapping from considered dates to relative number of days with respect to the date given via date_origin.

Argument	Domain	Note
D	number (1-31)	Day of Month
M	number (1-12)	Month
Y	number (1XXX-2XXX)	Year
Days	number (no restriction)	Number of Days

date_weekday/2( (D,M,Y), Weekday )

Mapping from considered dates to weekdays.

Argument	Domain	Note
D	number (1-31)	Day of Month
M	number (1-12)	Month
Y	number (1XXX-2XXX)	Year
Days	number (0-6)	Weekday

Weekdays are as follows: 0/Monday, ..., 6/Sunday

last_date_month/3( D,M,Y )

Gives the last date of a given month and year.

Argument	Domain	Note
D	number (1-31)	Day of Month
M	number (1-12)	Month
Y	number (1XXX-2XXX)	Year