Enter a start date and time and an end date and time to calculate the exact duration between two moments. Fill in Start Date/Time and End Date/Time fields and get back the total difference broken down into years, months, weeks, days, hours, minutes, and seconds — plus the total count in each unit.
Total Days
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Years
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Months
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Weeks
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Days (remainder)
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Hours
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Minutes
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Seconds
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Total Hours
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Total Minutes
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Total Seconds
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Enter your start and end date and time values, then the calculator computes the exact difference between them. It breaks the result down into years, months, weeks, days, hours, minutes, and seconds, and also shows the total duration expressed purely in days, hours, minutes, or seconds.
By default, the calculator counts from the start date up to but not including the end date — similar to how most calendars work. Checking this option adds one full day to the result, which is useful when you want to count both the first and last day as full days (for example, when calculating the length of an event that runs from Day 1 through Day 5 inclusive).
Yes, the calculator handles multi-year spans including leap years automatically. Time zone differences are not factored in by default; the calculator treats both date/time values as entered, so if your two times are in different time zones you should convert them to the same time zone before entering them.
The calculator accounts for leap years when computing the total number of days. February has 29 days in a leap year (divisible by 4, except centuries not divisible by 400), and this is reflected accurately in the day count.
'Total Days' shows the entire duration expressed as a pure number of days (e.g. 532 days). 'Days (remainder)' is the leftover days after subtracting full years, months, and weeks from the total — it is the 'd' component in a broken-down result like '1 year, 4 months, 2 weeks, 3 days'.
Different calculators handle month lengths (28–31 days) and whether to include the end date differently, which can produce slightly different month/week counts. Total days and total seconds should be consistent across tools, but the breakdown into years and months depends on the counting method used.
Absolutely. Enter the historical date and time as your start, and today's date and time as your end. The calculator will tell you exactly how long ago that event occurred, down to the second.
The calculator measures duration down to the second. The datetime-local input supports hour and minute precision; seconds are carried forward from the full timestamp, giving you a precise result to the nearest second.