RSDateSpan guides
Practical notes for date difference calculator, including examples and the limits of each workflow.
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Inclusive and exclusive day counting
The ordinary date difference from October 1 to October 4 is three days. It measures the number of day boundaries between the dates.
READ THE GUIDECalendar days are different from elapsed hours
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.