Recurrence & Events

A rule like "every 30 days" and a rule like "the second Tuesday of every month" both produce a repeating sequence of dates, but they behave very differently over time. This category covers generating and reasoning about recurring dates: next-occurrence lookups, every-N-days schedules, weekly and monthly rules, nth-weekday rules, and what happens when a recurrence rule lands on a date that does not exist in every month, like the 31st.

Fixed-interval recurrence drifts against the calendar

A rule anchored to a fixed number of days (every 14 days, every 30 days) walks steadily across the calendar: it will not land on the same weekday indefinitely, and "every month" is not the same as "every 30 days" over a long enough run, since months vary in length. A rule anchored to a calendar position (the last Friday of the month, the 15th) does not drift that way, but it does have to define what happens when the 15th falls on a weekend, or when "the 31st" lands in a month that stops at 30 or 28 days. Naming which kind of rule is in play, and what its edge-case behavior is, is the actual content of this category.

An exception is not a broken schedule

A recurring meeting that gets moved once, or a recurring payment that skips a holiday, is still one schedule with one documented exception, not a reason to abandon the rule. This category treats exception handling (skip, shift, or substitute) as part of the recurrence model itself rather than something a user has to work around by hand.

Where to go next

For a single non-repeating deadline or countdown, see Deadlines & Project Capacity. For a recurring event that needs to be shown in more than one time zone, see Time Zones & Meetings.