Calendar days are different from elapsed hours
Use dates for a date question
If you want the number of calendar days between two dates, local clock changes should not turn one day into a fraction. This calculator uses a UTC-based day index for that purpose.
Use timestamps for elapsed time
A question about hours between two actual events requires timestamps and timezone information. Calendar dates alone do not identify exact moments.
Check the input order
The end date must be on or after the start date. Invalid dates or a reversed range are reported instead of being silently changed to a positive number.
Try the workflow
October 1 to October 4 is a three-day difference. Counting both calendar dates inclusively gives four days.
Open date difference calculator