Date Difference Calculator
Find the number of days, weeks, months and years between two dates.
TL;DR — Date Difference Calculator: A date difference calculator computes the elapsed time between two calendar dates, expressed in multiple units — days, weeks, months and years. Use it for project planning, contract durations, leave management, deadline tracking and historical span calculations.
What is the Date Difference Calculator?
A date difference calculator computes the elapsed time between two calendar dates, expressed in multiple units — days, weeks, months and years. Use it for project planning, contract durations, leave management, deadline tracking and historical span calculations.
How to use the Date Difference Calculator
- Enter the start date.
- Enter the end date.
- Read the difference in days, weeks, months and years.
Formula
Days = (EndDate − StartDate) in milliseconds ÷ 86,400,000 Weeks = Days ÷ 7. Months and years calculated by calendar decomposition.
A "month" varies between 28–31 days, so calendar-month differences use date arithmetic, not a fixed 30 days.
Worked example
From 2024-01-15 to 2026-05-24: 860 days, ≈ 122.86 weeks, 2 years, 4 months and 9 days.
Frequently asked questions
How are months counted?
By calendar — going from Jan 15 to Feb 15 is one month, regardless of whether February has 28, 29, 30 or 31 days.
Does the calculator include both endpoints?
No — it counts the elapsed time. To include both start and end dates as full days, add 1.
How do I exclude weekends?
Cal44's date difference calculator counts calendar days. For working-day calculations, you can roughly multiply by 5/7 (assuming no holidays).
How many days are in a year on average?
365.2425 — accounting for leap years and the Gregorian calendar's 100-year and 400-year rules.
Can the end date be before the start date?
Yes. The calculator returns the absolute difference.