Date Calculator

How date calculation works

Years and months are applied first, as true calendar steps: adding 1 month to January 31 lands on the last day of February (the 28th, or 29th in a leap year), because February has no 31st. Days and weeks are then applied as plain day counts — a week is 7 calendar days — rolling correctly over month lengths, leap years, and year boundaries.

Weekdays-only mode counts the days & weeks part in business days instead: the calculator steps one day at a time and only counts landings on Monday through Friday. In this mode one "week" means 5 weekdays, so adding 1 week to a Wednesday lands on the next Wednesday, having skipped the weekend in between. Months and years still move as calendar steps. This is the mode to use for "10 business days from today" style deadlines — but note it does not skip public holidays, which vary by country and employer.

Common uses: contract and subscription end dates, project deadlines, pregnancy and leave planning, "90 days out" scheduling, and counting forward from a start date to a review or renewal date. For the gap between two known dates instead, use a days-between-dates calculator.