Add or Subtract Time

Add or subtract days, hours, minutes and seconds from any date and time. Get the exact resulting date in local and ISO formats.

Add / Subtract Time

Shift a date/time forward or backward by any combination of days, hours, minutes and seconds.

Base:

Days: Hours: Minutes: Seconds:

About the Add or Subtract Time

Shift a base date forward or backward by any combination of days, hours, minutes and seconds. The result shows the new date in human-readable local form (with day of the week) and ISO 8601 format.

Useful for scheduling deadlines, calculating delivery dates, planning meetings across time zones, and ad-hoc date arithmetic.

How it works

Your delta (days, hours, minutes, seconds) is converted into a single millisecond offset and then either added to or subtracted from your base date. Because it works in pure milliseconds, "add 1 day" always advances by exactly 24 hours — wall-clock time may shift by an hour if the result crosses a daylight-saving boundary.

Examples

Base: Mar 1, 2026 12:00 — add 30 daysMar 31, 2026 12:00
Base: Dec 31, 2025 23:59 — add 5 minutesJan 1, 2026 00:04
Base: Jul 4, 2025 09:00 — subtract 90 minutesJul 4, 2025 07:30

Frequently asked questions

Does this account for daylight saving time?

It works in pure milliseconds, so adding "1 day" always advances by exactly 24 hours. If the range crosses a DST boundary, the wall-clock time shifts by an hour. For DST-aware wall-clock arithmetic use the Time Zone Converter.

Can I add negative numbers?

No — use the Subtract button instead. The input fields only accept non-negative values.

How big a delta can I add?

Date arithmetic stays accurate to the millisecond up to roughly ±100,000 years from 1970, which is the full ECMAScript Date range.