Compute the first time after FIXED-TIME which matches RELATIVE-TIME.
This function finds the first moment after FIXED-TIME which honors every
element in RELATIVE-TIME:
(next-time @2007-05-20 (relative-time :month 3)) => @2008-03-20
The relative time constructor arguments may also be symbolic:
(relative-time :month :this)
(relative-time :month :next)
(relative-time :month :prev)
To find the date two weeks after next February, a combination of NEXT-TIME
and ADD-TIME must be used, since "next February" is a relative time concept,
while "two weeks" is a duration concept:
(add-time (next-time @2007-05-20 (relative-time :month 2))
(duration :days 14))
NOTE: The keyword arguments to RELATIVE-TIME are always singular; those to
DURATION are always plural.
The following form resolves to the first sunday of the given year:
(next-time (previous-time @2007-05-20
(relative-time :month 1 :day 1))
(relative-time :week-day 0))
This form finds the first Friday the 13th after today:
(next-time @2007-05-20 (relative-time :day 13 :day-of-week 5))
NOTE: When adding times, NEXT-TIME always seeks the next time that fully
honors your request. If asked for Feb 29, the year of the resulting time will
fall in a leap year. If asked for Thu, Apr 29, it returns the next occurrence
of Apr 29 which falls on a Friday. Example:
(next-time @2007-11-01
(relative-time :month 4 :day 29 :day-of-week 4))
=> @2010-04-29T00:00:00.000
- Package
periods
- Source
periods.lisp (file)