One month is not the same thing as 30 days
The main calculation works with days and seven-day weeks. If you mean “one calendar month later,” use the separate month/year helper instead.
FREE WEB TOOL
Add or subtract days/weeks from a date.
Add or subtract a whole number of days or weeks from a base date. One week is treated as exactly seven days. Month/year calendar arithmetic is available in the additional calculation area when month-end behavior matters.
2026-09-01 plus 30 days becomes 2026-10-01. Two weeks means 14 days, producing 2026-09-15.This is calendar-day arithmetic, not business-day arithmetic. Saturdays, Sundays and holidays count normally. Use a business-day calculator when working days are the requirement.
The main calculation works with days and seven-day weeks. If you mean “one calendar month later,” use the separate month/year helper instead.
Two weeks means 14 calendar days. The tool does not skip weekends or public holidays.
When the source date is the last day of its month, the month/year helper can keep the result at the destination month end rather than pretending every month has the same length.
The page works with local calendar dates only. It does not calculate hours, UTC offsets, daylight-saving transitions or time-zone differences.
Contracts and event schedules may say “30 days” or “one month,” which can lead to different dates. Use the mode that matches the wording of the real rule.
Related references: ISO 8601 · Date formats · World calendars