📅 Date Calculator
Find the difference between two dates, or add/subtract days from a date.
How This Works
Both modes use simple, exact calendar-day math. "Days Between Dates" counts the whole days between two calendar dates. "Add/Subtract Days" moves forward or backward from a starting date by the exact number of days you specify.
Frequently Asked Questions
Does this account for leap years?
Yes. Both modes use exact calendar-date arithmetic, which automatically accounts for leap years (including
February 29th) and varying month lengths.
Guide: understanding your result
- The number of days between two dates counts calendar days; decide whether the start and end dates are included, since legal and contract deadlines often exclude the first day.
- Business days exclude weekends and, if needed, public holidays. There are 11 federal holidays in the United States.
- Adding months is not the same as adding 30 days: January 31 plus one month lands on the last day of February.
Worked example
From January 1 to March 1, 2026 is 59 days (2026 is not a leap year). Adding 90 days to November 14, 2026 gives February 12, 2027.
US federal holidays
| Holiday | Date |
|---|---|
| New Year's Day | January 1 |
| Martin Luther King Jr. Day | 3rd Monday in January |
| Washington's Birthday | 3rd Monday in February |
| Memorial Day | Last Monday in May |
| Juneteenth | June 19 |
| Independence Day | July 4 |
| Labor Day | 1st Monday in September |
| Columbus Day | 2nd Monday in October |
| Veterans Day | November 11 |
| Thanksgiving Day | 4th Thursday in November |
| Christmas Day | December 25 |
When a fixed-date holiday falls on a weekend, federal offices usually observe it on the nearest weekday.
Common mistakes to avoid
- Forgetting leap years (February 29).
- Mixing calendar days and business days in deadlines.
Frequently asked questions
Which years are leap years?
Years divisible by 4, except century years not divisible by 400. 2028 is a leap year; 2100 is not.
Official sources
Examples are calculated live from the same data the calculator uses and are for education only — they are not financial, tax or investment advice.
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See all →✔ Reviewed by GelirLab Editöryal Ekibi · How we check our calculators