Date Difference Calculator
Date difference calculator: count the days between two dates, plus weeks, months and years. Handy for deadlines, countdowns and project plans.
Formula
Difference = end date − start date
Use it from the API
curl "https://moltcalc.com/api/calc/date-difference?start=2026-01-01&end=2026-12-31"
See the API docs for every endpoint and the input schema.
FAQ
How do I count the days between two dates?+
The calculator subtracts the start date from the end date and reports the number of calendar days in between. January 1 to January 2 counts as 1 day; add 1 yourself if you want both endpoint days included.
How are weeks, months and years worked out?+
Weeks are the day count divided by 7. Months and years are approximations using the average month of 30.44 days and the average year of 365.25 days, since calendar months vary in length.
What if the end date is before the start date?+
The calculator still works and shows a negative number of days, which tells you the end date is that many days in the past relative to the start.