Dates and ages
Age, elapsed dates, countdowns and calendar arithmetic.
Calculator topic hub
Date and time calculators
Calculate ages, date differences, countdowns, working days, clock arithmetic, durations and world times.
Most useful tools
Age calculatorCalculate age from any birth date.Date differenceCount days, weeks or months between dates.Time duration calculatorCalculate elapsed hours and minutes between two clock times, including an overnight interval.Business days calculatorCount weekdays between two dates.Add time calculatorAdd a duration to a 24-hour clock time and show any day rollover.Add or subtract date calculatorAdd positive days or subtract negative days from a calendar date.
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Working and calendar days
Business days, ISO week numbers and weekdays.
Clock time and durations
Elapsed time, time addition, subtraction and unit totals.
Zones and timestamps
Location-aware time conversion and Unix time.
About these tools
Calendar calculations use UTC date-only arithmetic and calendar-aware rules rather than dividing days by fixed year or month lengths. Clock-duration tools deliberately avoid timezone logic; the time-zone converter uses IANA rules when an actual instant and location matter.
All tools in this category
Age calculatorCalculate age from any birth date.Date differenceCount days, weeks or months between dates.Days until calculatorCount down to any future date.Business days calculatorCount weekdays between two dates.Time zone converterConvert a local date and time between IANA time zones.Days between dates calculatorCount exact elapsed calendar days and weeks between two dates.Hours calculatorCombine hours and minutes into decimal hours and total minutes.Minutes calculatorCombine hours, minutes and seconds into total minutes.Add or subtract date calculatorAdd positive days or subtract negative days from a calendar date.Week calculatorFind the ISO week number and week-year for any date.Month calculatorCount completed calendar months and total elapsed days between dates.Birthday countdown calculatorCount calendar days until the next occurrence of a birthday.Day of week calculatorFind the weekday for any Gregorian calendar date.Unix timestamp converterConvert a UTC date and time into Unix seconds and milliseconds.Add time calculatorAdd a duration to a 24-hour clock time and show any day rollover.Subtract time calculatorSubtract a duration from a 24-hour clock time and show any previous-day rollover.Time duration calculatorCalculate elapsed hours and minutes between two clock times, including an overnight interval.