subtract-duration

Arguments: date-timespec durationspec

Returns a new date-time object obtained by subtracting the duration specified by durationspec from the date-time specified by date-timespec.

The default method does not subtract two durations.

 > (require :datetime)
 > (use-package :util.date-time)

 > (subtract-duration (date-time "1985-04-10T10:30:40") 
         (duration "1MT1H4S"))
 #<date-time "1985-03-10T09:30:36" @ ...>

See duration, date-time, and add-duration.

See date-time.htm for information on support in Allegro CL for parsing and generating time expressions using the ISO 8601 standard. See particularly the section Adding/Subtracting Durations, where it is pointed out (with examples) that adding and subtracting durations are not inverse operations and adding durations is not associative.

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This page was not revised from the 10.0 page.
Created 2019.8.20.