- How is month arithmetic handled?
- Adding N months keeps the day-of-month, clamped to the last day of the target month. For example, January 31 + 1 month is February 28 or 29.
- Is the difference inclusive?
- Yes. Both the start and end date count toward the total days figure, matching the common interpretation of “how many days between these two dates.”
- How are leap years handled?
- Date arithmetic uses the Gregorian calendar. Leap years and month lengths are respected automatically.