Next Occurrence of a Weekday Calculator

How it works

forward: days = (target weekday − start weekday + 7) mod 7 · backward: days = (start weekday − target weekday + 7) mod 7 · if that is 0 and the start date is skipped, use 7 · nth occurrence = first + (n − 1) × 7 days · result = start date ± days

Weekdays repeat every 7 days, so the gap to the next Monday (or any weekday) is the difference between the two weekday numbers (Sunday = 0 … Saturday = 6), wrapped around the week with mod 7. Looking back works the same way in reverse, which gives the date of last Friday or the most recent Sunday. If the start date already falls on the chosen weekday you decide whether it counts (0 days) or whether you want the same day a week later. “Which occurrence” jumps further ahead — 2 gives the Monday after next, 4 gives the fourth Monday from now — and the schedule table lists the dates that follow every week or every 2, 3 or 4 weeks, with the ISO week number of each, which is handy for classes, rotations, fortnightly paydays or bin collection.

Worked example

Starting from Wednesday, September 16, 2026 and asking for the next Monday: Monday is 1 and Wednesday is 3, so (1 − 3 + 7) mod 7 = 5 days away — Monday, September 21, 2026, in ISO week 39. The Monday after next (occurrence 2) is 5 + 7 = 12 days away, on September 28. Looking back instead, the last Monday was (3 − 1 + 7) mod 7 = 2 days earlier, on September 14. A schedule every 2 weeks from September 21 continues October 5, October 19 and November 2.

Frequently asked questions