Date Calculator
Find the difference between two dates — or add / subtract days from a starting date.
Years
0
Months
0
Days
0
Total days
0
Total weeks
0 weeks, 0 days
Two modes, one job
The Date Calculator combines the two most-searched date questions into one tool. Use Date difference when you have two known dates and want to know how far apart they are — for age, project timelines, notice periods, warranty windows or contract terms. Use Add / subtract days when you know a starting date and need to find the exact calendar date some number of days before or after it — deadline planning, delivery estimates, or working out a due date.
Why the answers are correct
For the difference, we use two representations: the total number of calendar days between the two dates (the answer to "how many days"), and the same range broken into years, months and days using calendar-borrow arithmetic — the same rule official forms use for age. Add / subtract uses native JavaScript date arithmetic, which correctly accounts for month lengths, leap years and DST changes.
Real-world uses
- How many days until my exam / interview / event?
- Notice period ends on what date if I resign today?
- Warranty expires when if it started on a given date + 730 days?
- Baby delivery date estimated as last-period + 280 days.
- Legal deadline: filing due 90 days after the notice.