Free Online Date & time Tools
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Date & time
1–12 / 20Add or subtract calendar days
Shift a Gregorian date by an integer number of UTC calendar days.
Add calendar months
Shift calendar months, clamping to the last valid day of the destination month.
Business day count
Count Monday–Friday dates including both endpoints, excluding supplied holidays; max 20000 calendar days.
Add business days
Move forward or backward by Monday–Friday workdays, excluding the starting date and supplied holidays.
ISO week number
Find ISO week-year, week number and weekday (Monday=1, Sunday=7).
Day of year
Find ordinal day, total year length and days remaining after the given date.
Leap year checker
Check the proleptic Gregorian century and 400-year leap rules.
Unix timestamp converter
Convert Unix seconds/milliseconds and ISO timestamps with explicit timezone offsets.
Time zone at an instant
Display a fully specified instant in an IANA timezone, applying the browser’s daylight-saving database.
Add clock durations
Sum nonnegative HH:MM:SS durations; hours may exceed 23.
Elapsed time between instants
Calculate precise elapsed time between ISO timestamps, honoring explicit offsets.
Monthly calendar grid
Build a Gregorian calendar with Monday-first weeks and null outside-month cells.
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