📅 Date & Time Calculator
Date difference, age, countdown, time unit conversion, Excel serial time, decimal hours, and duration adder.
About Date & Time Calculator
Dates and durations come up constantly in work — project deadlines, contract terms, age verification, payment schedules. This tool packs all the essential date and time calculations into one place: calculate the exact difference between two dates, find someone's precise age, set up a countdown, convert between time units, work with Excel serial dates, convert decimal hours to hours and minutes, and add or subtract durations.
Instead of juggling a calendar, a stopwatch, and a spreadsheet formula, everything is right here. Whether you're doing financial planning, project scheduling, payroll calculations, or just counting down to a vacation, this calculator covers it without any setup.
Type a value in any field — all others update instantly.
Integer part = date (days since Jan 0 1900). Fractional part = time of day (0.5 = 12:00:00).
Convert between decimal hours (e.g. 1.5 h) and HH:MM:SS (1:30:00). Useful for timesheets and billing.
Add or subtract multiple durations. Format: 1h30m, 1h30, 45m, 2h, 90s, or HH:MM:SS.