Date & Time · Dates
Formula verified
Date Calculator
Two calculators in one: work out the gap between two dates, or find the date a given number of days before or after another.
Mode
Days between
262 days
2026-01-01 → 2026-09-20
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Two ways to work with dates
"Days between" counts how many days it takes to get from one date to another — useful for deadlines, countdowns, and figuring out how long ago something happened. "Add or subtract days" runs the other direction: starting from a known date, it finds what date you land on some number of days later (or earlier, with a negative number).
The formula
days between = end date − start date · new date = start date ± N days
Worked example
From January 1, 2026 to September 20, 2026 is 262 days. Ninety days after January 1, 2026 is April 1, 2026.
Frequently asked questions
Does the days-between count include both the start and end date?
No — this calculator counts the number of days you'd need to move forward from the start date to reach the end date, which is the exclusive count (the same one a due-date or age calculation uses). If you want an inclusive count of calendar days touched, add 1 to the result.
Can I subtract days instead of adding them?
Yes — enter a negative number of days in the add/subtract mode and it moves backward from the starting date instead of forward. The same underlying date arithmetic handles both directions.
Why does the years/months/days breakdown differ from dividing the day count by 365?
Dividing by 365 ignores leap years and the fact that months have different lengths, so it drifts by roughly a day every four years. The years/months/days breakdown instead counts whole calendar years, then whole calendar months, then whatever days are left over — the same calendar-aware method the Age Calculator uses.
Sources and method
- Calendar arithmetic and the Gregorian leap-year rule — general published mathematics and civil calendar standards.