Sounds useful.

In addition to fixing PHPStan, we also need:

• tests for this new method
• updated user guide
• changelog entry

Happy to write tests/docs/changelog.

I had tried returntype Time brefore but this also returns an error. Functions like addMonth() do not have any return type specified. What is the correct type?

Is there a way to run PHPStan only on one file, or does this break the testing? composer phpstan:check system/I18n/TimeTrait.php does not return any errors.

For phpstan, you should run it on the whole codebase, not just the changed file.

For testing, you can just add your example as a data provider then test on them.

Initial date: 2025-01-31
+---------+------------+-------------------+
| $months | addMonths | addCalendarMonths |
+---------+------------+-------------------+
| 0 | 2025-01-31 | 2025-01-31 |
| 1 | 2025-03-03 | 2025-02-28 |
| 2 | 2025-03-31 | 2025-03-31 |
| 3 | 2025-05-01 | 2025-04-30 |
| 4 | 2025-05-31 | 2025-05-31 |
| 5 | 2025-07-01 | 2025-06-30 |
| 6 | 2025-07-31 | 2025-07-31 |
| 7 | 2025-08-31 | 2025-08-31 |
| 8 | 2025-10-01 | 2025-09-30 |
| 9 | 2025-10-31 | 2025-10-31 |
| 10 | 2025-12-01 | 2025-11-30 |
| 11 | 2025-12-31 | 2025-12-31 |
| 12 | 2026-01-31 | 2026-01-31 |
| 13 | 2026-03-03 | 2026-02-28 |
+---------+------------+-------------------+

For phpstan, you should run it on the whole codebase, not just the changed file.

For testing, you can just add your example as a data provider then test on them.

Thank you, I figured out I need to run on the whole code base. Error should be gone now.

I wrote tests similar to testCanAddMonths() etc. I used a date that with a result in February.

Thank you, @christianberkman 🎉