How to Calculate Days Between Two Dates: Rules and Examples
When you need to measure the time between two events, check the length of a period, or simply find out how many days separate two dates, the first step is to define the counting rule. “Days between dates” can mean the number of elapsed calendar days, or the number of calendar dates in a period when both boundaries are counted. For most date-difference calculations, the start date is the reference point and the end date is not added as a separate day by default. That is why 1 September to 5 September is 4 days, not 5. This guide explains that convention, inclusive counting, leap years, reversed..