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Adding durations with year or month components convert to weeks #751
Description
- I am on the latest Pendulum version.
- I have searched the issues of this repo and believe that this is not a duplicate.
- OS version and name: Linux pop-os 6.4.6-76060406-generic #202307241739
169462191722.04~ac5e1a8 SMP PREEMPT_DYNAMIC Wed S x86_64 x86_64 x86_64 GNU/Linux - Pendulum version: 2.1.2
Issue
When adding two durations together, if one has a years or months component, that is converted into weeks instead. e.g.
>>> pendulum.duration(years=2) + pendulum.duration(days=1)
Duration(weeks=104, days=3)
>>> pendulum.duration(months=2) + pendulum.duration(days=1)
Duration(weeks=8, days=5)This also means that addition of durations is non-commutative
>>> ( pendulum.datetime(2023, 1, 1) + pendulum.duration(years=1) ) + pendulum.duration(years=1)
DateTime(2025, 1, 1, 0, 0, 0, tzinfo=Timezone('UTC'))
>>> pendulum.datetime(2023, 1, 1) + ( pendulum.duration(years=1) + pendulum.duration(years=1) )
DateTime(2024, 12, 31, 0, 0, 0, tzinfo=Timezone('UTC'))
Activity
tempookian commentedon Mar 22, 2024
I think the behavior you've encountered is intentional due to different operations for
+betweenDurationobjects and betweenDateTimeandDuration. ForDuration+Duration, both durations are converted to seconds, combined, and formed into a newDuration. But, when adding aDurationto aDateTime, it directly increases theDateTimecomponents, likeyear, based on the duration's equivalent. To ensure consistency, especially with variable-length units like years, convertDurationtotimedeltafirst: