EpochLab

Subtract Months

What date was N months ago?

Months taken off on the calendar, with the shorter-month case clamped and stated — and a warning that month arithmetic does not reverse cleanly.

Questions people ask

The things that come up about subtract monthss, answered plainly.

Why does adding a month and subtracting one not return me to the start?

Because clamping loses information. 31 March minus one month is 28 February; adding a month back gives 28 March, not the 31st. Every date library behaves this way, and it is worth knowing before you build a billing schedule on it.

Related tools

Move a date forwards or backwards by a span, with the calendar's rules applied.

All 160 tools · More in add & subtract