Date & Time Calculators
Calculate ages, durations, workdays, time zones and more — accurate to the second and aware of leap years and DST.
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All date & time calculators (10/10)
About date & time calculators
Working with dates is surprisingly tricky: leap years, varying month lengths, daylight saving and time zones all complicate simple arithmetic. Our date and time calculators handle these edge cases automatically. The age, date-difference and time-duration calculators give exact spans in years, months, days, hours, minutes and seconds. The workday calculator excludes weekends (and optional holidays). The time-zone calculator converts between any two IANA zones with current DST rules. Time card and hours calculators help track worked time, sleep helps plan rest, and countdown counts down to any moment.
Why use our date & time calculators?
Correctly handles February 29 and varying month lengths.
Uses the IANA time-zone database for accurate cross-zone conversion.
The workday calculator supports custom holiday lists.
Durations down to seconds, not just days.
Countdown updates every second without reloading.
Calculate dates from year 1 to year 9999.
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View all →Frequently asked questions
How is age calculated?▾
We compute the exact number of complete years, then the remaining months, then the remaining days — accounting for varying month lengths and leap years.
Do time-zone calculations include DST?▾
Yes. We use the browser's IANA time-zone database, which knows historical and current daylight-saving rules for every region.
How are workdays counted?▾
By default, Saturday and Sunday are excluded. You can also add custom holiday dates.
What's the difference between time card and hours calculator?▾
Time card tracks clock-in/clock-out periods for shifts; the hours calculator adds and subtracts arbitrary durations.
How precise is the sleep calculator?▾
It uses 90-minute REM cycles to suggest bedtimes that align with natural wake points.
Can I countdown to a past date?▾
Yes — if the target is in the past it shows how long ago it was; if in the future, time remaining.