Days Between Dates Calculator
Calculate the exact duration between two calendar dates. Useful for verifying contract periods, payment milestones, interest day counts, and overdue aging intervals.
How it works
Days difference = (end timestamp − start timestamp) in milliseconds ÷ 86,400,000 milliseconds per day. From 1 January 2026 to 31 January 2026 there are exactly 30 elapsed days (approximately 4.3 weeks).
Questions
Does the count include both the start and end dates?
By standard business convention, it measures elapsed intervals between dates. Add one day if your billing contract explicitly requires inclusive boundary counting.
Does this calculator adjust for leap years?
Yes. Standard calendar calculations account for Gregorian leap year February days across any selected historical or future year span.
What happens if the start date is after the end date?
The calculation evaluates absolute elapsed duration in days regardless of which order the dates are specified.
Results are estimates for planning. They are not tax, legal or financial advice.
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