How to use this calculator
Choose Days between and enter a start and end date. Select Include both dates to count both calendar dates. Or choose Add or subtract days and enter a signed whole number: positive adds days, negative subtracts days. Use today fills the start date from your device.
The math behind it
Day difference = end calendar day − start calendar day Inclusive count = signed difference with one extra day in the same direction Shifted date = start calendar day + signed day offset
A worked example
January 1 to January 31 is 30 elapsed days, or 31 when both dates are included. Adding 1 day to February 28, 2024 gives February 29, 2024. Subtracting 1 day from January 1 gives December 31 of the previous year.
Assumptions & precision
Gregorian dates in years 0001–9999. All days count, including weekends and holidays. End dates before start dates produce negative results; inclusive mode keeps that sign. The same date gives 0 elapsed days or 1 inclusive day. Offsets must be whole numbers from −3,652,058 to 3,652,058 and the resulting date must remain in range. Date-only arithmetic uses UTC internally to prevent daylight-saving shifts; it does not measure hours or time-zone-dependent elapsed time. Output dates use YYYY-MM-DD.
A common question
Does this count business days?
No. This counts every calendar day, including weekends and holidays. It does not apply work schedules or holiday calendars.