Multi-Date Offset Calculator

Worked example

January 30 and January 31, 2027 both plus 1 month land on February 28. Neither day exists in February, so both are constrained to its last valid day, even though they started on different days. Add a third date, January 15, 2027, to the same list, and it lands on February 15 with no constraint at all, since February 15 is a completely ordinary date. The result table shows all three outcomes side by side, so the pattern of which dates get constrained and which do not is visible at a glance.

Common mistakes

• Assuming every date in a list shifts by the same visible amount. Two dates that started only a day apart can land on the exact same result once month-end constraint kicks in for both, collapsing what looked like a one-day gap.
• Missing which rows were actually constrained. The flag column exists precisely because a constrained result looks identical to an unconstrained one unless it is checked against the original date.

Limitations

This applies one offset to up to 50 dates using the constrain rule. It does not support a different rule per date or a per-date custom offset, so a list that needs mixed rules has to be split and run through separately for each rule.