How date difference calculator works
This calculator finds the exact difference between two dates. It parses both dates at midnight (00:00:00) and computes the difference in milliseconds, then converts to days by dividing by 86,400,000 (the number of milliseconds in a day). Weeks are the whole weeks within that span, with the remainder shown as extra days.
The total hours and minutes are also computed, useful for time-sensitive calculations like project deadlines or elapsed time. For longer spans, approximate years and months are derived from the day count using the average year length (365.25 days, accounting for leap years) and average month length (30.44 days).
The result works for dates in either order. If the end date is before the start date, the days value will be negative. This can be useful for counting down to a deadline (negative) or counting up from a past event (positive).