ReKnock Recurring Tasks: Research

Short comparison of how five popular task apps handle repeating tasks, and what ReKnock should copy. Written from product knowledge, not re-verified against live apps today. Details change, so treat each cell as "what I believe", not gospel.

The three questions that matter

Fixed vs after-completion. Does the next one come from the calendar ("every 28th") or from when you actually did it ("30 days after I last did it")?
How do you enter it? Pickers only, or plain English ("every last Friday")?
Can you skip one? Or stop the series cleanly?

Comparison

	Fixed schedule	After completion	Plain-English input	Skip one	End condition	Lead time
Todoist	Yes: `every 28th`	Yes: `every! 30 days`	Excellent, the benchmark	No dedicated skip; workaround is complete or reschedule	`until`, `for N weeks`	No
TickTick	Yes (default)	Yes: "repeat from completion date"	Good, parses it from the title	Has a skip action	End date or count	Reminder offsets only
Things 3	Yes: "repeat on a schedule"	Yes: "repeat after completion"	Little or none	No skip. You can delete one or stop repeating	Optional end	Yes: "add N days before deadline"
Google Tasks	Yes	No	No	No	Date or count	No
Apple Reminders	Yes, with custom N units and "last Friday" style monthly	No	Via Siri	No ("delete this and future" only)	End date	No

What they do on completion

All five keep one live task and move it forward (or create the next copy). None build a backlog of missed ones for daily or weekly tasks.
Todoist and TickTick, when you complete an overdue fixed task, jump to the next future occurrence. That is the behavior people expect and the one ReKnock wants.
Things and TickTick show the next item early (Things hides it until the lead window). Matches ReKnock's start_date: quiet until it is time.

Lessons

Both modes are needed. Card minimums and smoke alarms are fixed. "Oil change every 6 months" and "30 days after I did it" are after-completion. Only Todoist, TickTick and Things offer both, and Rob has examples of each.
Lead time is a real feature. Things proves the value ("show it 3 days before the deadline"). ReKnock already has start_date, so lead time falls out for free.
Plain English wins on voice. ReKnock is used through MCP and voice. A deterministic parser for common phrases, backed by a structured form, fits that.
Skip is underserved and cheap. Everyone gets this wrong. Nagging apps need it more than others, because an un-skippable occurrence keeps knocking.
Month-end handling is rarely documented. Calendar RFC 5545 skips months that lack a 31st. People find that surprising. Clamping to the last day matches expectation for "pay on the 31st".

Recommendation

One live task row per series. On completion, log a done-history snapshot and push start_date (and due_date) to the next occurrence. Same id, text, contexts, nag times, quadrant. Reuses ReKnock's existing "quiet until start_date" mechanism, so almost no new nagging logic.
Store the rule as an RFC 5545 RRULE subset (FREQ, INTERVAL, BYDAY incl. ordinals like -1FR, BYMONTHDAY, BYMONTH, UNTIL, COUNT), plus ReKnock fields for mode and lead_days. Interoperable and well specified. Deviate in one place: clamp short months instead of skipping.
Two modes: fixed (default) and after_completion.
Always jump to the next future occurrence. Never create a backlog.
Skip + stop as first-class actions (skip_occurrence tool, stop_series on done, repeat: none on update).
Input: structured repeat object (canonical) and a repeat_text plain-English helper, parsed by a small deterministic grammar that echoes back its interpretation so a voice user can confirm.
Lead time as lead_days, mapped to start_date = occurrence - lead_days.
Do not use an LLM to parse repeat text server-side. The calling assistant already is one. Keep the server deterministic and testable.