Date Adder

How It Works

Every calculation is done on plain calendar dates pinned to 12:00 UTC — never to your device's local midnight. That small trick removes the whole class of daylight-saving bugs: a DST day is 23 or 25 hours long locally, so midnight-based arithmetic drifts off by one around the switchovers, while noon-to-noon math over UTC's fixed 86 400-second days is exact. The final date is then rendered with Intl.DateTimeFormat in your locale, so the layout matches your language without touching the arithmetic.

Month jumps and the February 29 rule

Adding months or years keeps the day-of-month when the target month has it. When the target month is shorter, the date clamps to its last day and the page says so: February 29 plus one year in a non-leap year becomes February 28 (the same clamp that turns the 31st into the 30th in April). There is no reverse expansion — February 28 plus a year stays February 28 even when a leap year waits at the end.

Workdays: the exact rule

With 'skip weekends' on and the unit set to days, the counter steps one calendar day at a time and only counts days from Monday to Friday; Saturdays and Sundays are jumped over, not banked. If your start date is itself a weekend, the first counted workday is the Monday after it. Holiday calendars are deliberately not included.

Including the start date

The toggle changes the distance counts, not the result: with it on, the start date itself counts as day one in both the calendar-day and weekday totals, and the weeks-and-days breakdown shifts with them. It is the difference between 'thirty days from today' and 'day 30 including today', which is how contracts and due-date lists often speak.

Frequently Asked Questions