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To find the duration between two dates and times, enter both date-time values in a calculator that reports elapsed days, hours, minutes, and seconds. If the endpoints are in different time zones—or the interval crosses a daylight saving time change—use a calculator that accepts locations and explicitly accounts for those changes. The answer depends on whether you want elapsed time, calendar years and months, or working days.
Calculate the duration between two dates and times
A date-and-time duration calculator subtracts one point in time from another and can express the interval in days, hours, minutes, and seconds. Time and Date AS describes its Time Duration Calculator as finding “the number of days, hours, minutes, and seconds between 2 given points in time.” Its ordinary calculator does not account for daylight saving time (DST) or leap seconds, so check its limitations before using it for an interval affected by either. Time and Date AS: FAQ, Time Duration Calculator
- Choose a calculator that accepts the precision you need: dates alone, or dates with hours, minutes, and seconds.
- Enter the start and end date-times. Make sure you have not reversed them and that both values use the intended time zone.
- Read the result in the units that answer your question. Days, hours, minutes, and seconds describe elapsed time; years, months, and days use calendar rules.
Choose the right meaning of “duration”
| What you need | Use | What to check |
|---|---|---|
| Exact elapsed interval | A calculator that reports days, hours, minutes, or seconds | Whether it accounts for time zones, DST, and leap seconds if relevant. Time and Date AS says its ordinary calculator does not account for DST or leap seconds. Time and Date AS |
| Calendar age or time between dates in years, months, and days | A calendar-based calculator or spreadsheet function with calendar units | Months have different lengths, so the result depends on how the tool applies calendar units. |
| Working days between dates | A business-day calculator | Whether weekends and the relevant holidays are excluded. Time and Date AS provides a separate business-day calculator. Time and Date AS |
| Two locations or time zones | A cross-time-zone duration calculator | Whether the tool uses the locations’ time zones and accounts for DST switches. Time and Date AS says its separate calculator does. Time and Date AS |
Why years and months can look wrong
A month is a calendar unit, not a fixed number of days. A tool that breaks an interval into years, months, and days must decide how to add those units when a month ends before the same day number arrives in the next month. That can make a calendar breakdown look surprising even when the total elapsed days are correct.
Time and Date AS says its calculator applies larger units before smaller ones. In its common-year examples, January 28 to March 1 is one month and one day; January 31 to March 1 is also one month and one day, because adding a month to January 31 lands on February 28 before the remaining day is counted. There is no single perfect way to express every interval in months and years because calendar months vary in length. Time and Date AS: FAQ, Time Duration Calculator
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- Perpetual calendar
Time zones, daylight saving time, and leap seconds
When both times use one time zone
For a straightforward elapsed-time calculation, an ordinary duration calculator may be suitable when both inputs are understood in the same time zone. Do not assume every calculator handles clock changes: Time and Date AS says its ordinary calculator does not account for DST. If the interval crosses a DST change, the wall-clock difference may not match the elapsed time.
When the times are in different locations
Use a calculator that accepts the locations or time zones for both endpoints and explicitly handles DST. Time and Date AS directs users to its separate time-zone duration calculator for this case and says that tool accounts for DST switches. Time and Date AS: Time Zone Duration Calculator
Rank #2
- Future date determination for loans and transactions on left page.
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Leap seconds
Time and Date AS says its ordinary Time Duration Calculator does not account for leap seconds. That limitation applies to that calculator; it should not be assumed of every duration tool. Time and Date AS: FAQ, Time Duration Calculator
Recommended Free Tools
Calculate date differences in Google Sheets or Excel
Google Sheets
Google Sheets documents DATEDIF(start_date, end_date, unit) for whole years (Y), whole months (M), days (D), and remainder units (MD, YM, YD). Choose the unit that matches the question: a whole-month count is not the same as elapsed days. Google notes that months and years count only when the end date reaches or passes the start date’s day number; its example gives four months between September 30, 2015 and February 28, 2016. A numeric result can display as a date if the cell uses Date formatting, so change the number format when the result appears unexpected. Google Docs Editors Help: DATEDIF
Rank #3
- Easily identifies and calculates the number of weeks from a date with a simple in-hand tool
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Excel
Microsoft documents DATEDIF for calculating full days, months, and years, including combinations used for age or service calculations. It warns that the function supports older Lotus 1-2-3 workbooks, can calculate incorrectly in some scenarios, and specifically advises against the MD argument when accuracy matters. Do not rely on an MD-based years-months-days formula as universally accurate. Microsoft Support: Calculate the difference between two dates
For elapsed time between date-time values, make sure the spreadsheet result is formatted as a duration rather than a date or time of day. A spreadsheet formula does not by itself establish how different time zones or DST transitions should be interpreted; confirm those separately when they affect the inputs.
Quick Recap
Best Value
- This monthly desk pad calendar covers 12 months from January 2027 — December 2027 with Julian dates
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