The Date Difference Calculator does two everyday jobs. It tells you the time between two dates, and it can add or subtract days, weeks, months, or years from a date to land on a future or past date.

Days between two dates

Pick a start and end date and you get the gap in days, along with the same span shown in weeks, months, and years. For example, from 1 January to 31 December in a normal year is 364 days. This is handy for counting notice periods, project durations, or how long until an event.

Add or subtract from a date

Choose a date, then add or subtract an amount — say "90 days after today" or "6 months before a deadline" — and the calculator returns the exact date and the day of the week it falls on. When you add months or years, the day of the month is kept wherever the calendar allows.

Accurate by the calendar

Leap years are handled automatically, so February's extra day is always counted. Everything is computed from the calendar itself, not rounded.

Nothing you enter is uploaded — the calculation runs in your browser session, and any saved entries stay on your own device.