Add or subtract from a date
“Ninety days from today”, a notice period, a warranty expiry — pick a date, pick an offset, get the answer with its weekday.
Adding months is not adding 30 days
Calendar months and fixed day counts are different operations. One month after 31 January is 28 February in most years, because the target month has no 31st. Ninety days after the same date is 1 May. Contracts and legal notice periods usually mean calendar months, while delivery and payment terms usually mean days — the wrong reading can move a deadline by several days.
Years work the same way, which matters for one date in particular: a year after 29 February on a leap year lands on 28 February, since the target year has no 29th.
The weekday of the result is shown because it is often the real question. A deadline landing on a Saturday usually means the effective deadline is the Friday before or the Monday after, depending on the agreement.
Questions
How are months counted?
As calendar months. Adding one month to 31 January gives 28 February (or 29 in a leap year) because February has no 31st. Use days if you need a fixed count.
Can I combine units?
Yes — fill in several fields and they apply together. Years and months are applied first, then weeks and days, which is the conventional order.
Does it skip weekends?
No, this counts every calendar day. Use the business days calculator for working-day counts.