Date Add and Subtract Calculator
Add or subtract days, weeks, months or years from a date to find a new one.
A date, shifted by a period
Given a date and a period to move forward or back, this finds the resulting date — a fortnight from now, ninety days ago, eighteen months from a start. It handles the calendar's irregularities so the result is correct.
Enter a date and the period to add or subtract.
The calendar's awkward edges
Shifting a date by hand is error-prone because the calendar is not uniform: months vary in length, leap years insert a day, and adding months creates genuine ambiguities — a month after the 31st has to land somewhere sensible in a shorter month. Counting a large number of days across these boundaries is exactly where mistakes happen. The calculation navigates all of it automatically. This is the everyday tool behind working out renewal dates, deadlines, notice periods, warranty expiries and any planning that starts from a known date and moves a set amount. Because the calendar's irregularity makes it so easy to be a day or two off by hand, getting the exact date from a period is one of those quietly useful things worth having done reliably.
Common questions
Why is adding a period to a date error-prone by hand?
Because months vary in length, leap years add a day, and adding months across boundaries is ambiguous — like a month after the 31st landing in a shorter month.
What is it used for?
Renewal dates, deadlines, notice periods and warranty expiries — anywhere you start from a known date and move a set period.
Is anything uploaded?
No. The calculation happens in your browser.