How to use this calculator
Elapsed-day mode suits durations such as hotel nights. Inclusive mode counts the actual dates on a calendar.
The end date must be on or after the start date. Date-only arithmetic prevents daylight-saving changes from adding or removing a day.
The formula
Elapsed days = end date − start date. Inclusive count = elapsed days + 1.
A worked example
1 September to 15 September is 14 elapsed days, or 15 calendar dates including both endpoints.
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