A delay action takes exactly one of for (a duration measured from the moment the task is entered) or until (an instant), plus an optional tz both resolve against.

  - id: wait_two_hours
    action: {type: delay, for: 2h}
    switch: next

  - id: wait_until_monday
    action: {type: delay, until: "mon 09:00", tz: Europe/Prague}
    switch: next

The same grammar is an action’s timeout — a timeout is this syntax aimed at a deadline rather than at a wake-up. Exactly one of the two slots, never both and never neither: there is no default, and an absent slot is not zero.

for — a duration

A sequence of number-and-unit pairs, in any order: 2h30m, 7d, 1mo15d. An unquoted number is milliseconds, so for: 30000 is thirty seconds — quoted, it is refused, because "30000" is as likely to have meant seconds.

Unit	Means	Kind
ms	milliseconds	fixed
s	seconds	fixed
m	minutes	fixed
h	hours	fixed
d	days	calendar
w	weeks	calendar
mo	months	calendar
y	years	calendar

Fixed units are elapsed time; calendar units are calendar arithmetic in tz, and calendar units apply first whatever order they were written in. So 1d is “the same wall clock tomorrow” — 23 or 25 hours across a daylight-saving boundary, not 24. Month arithmetic clamps to the end of the target month, so 31 January plus 1mo is 28 or 29 February rather than rolling into March.

until — an instant

Four closed forms, and natural language is deliberately not among them:

Form	Example	Notes
absolute instant	2026-09-01T08:00:00Z	RFC 3339; carries its own zone, so tz is not consulted
wall clock	2026-09-01 08:00	no zone, so it is read in tz
offset plus wall clock	+2d 08:00	that many days on, at that time
calendar pattern	*-*-01 08:00, mon 09:00, *:*:0/5	the next match after now

The pattern form is the systemd OnCalendar subset: * is any, 0/5 is every fifth from zero, and a three-letter weekday (mon…sun, any case) selects a day.

tz

An IANA name (Europe/Prague), the literal UTC, or a fixed offset (+02:00). Absent means UTC.

Abbreviations such as CET and the special name Local are refused on purpose: an abbreviation denotes the wrong thing for half the year, and Local resolves against the host’s zone database — so the same definition would mean different things on two workers.

Two wall clocks have no single answer, and each has a rule. A time that does not exist, because the clock jumped forward over it, normalizes forward. A time that happens twice, because the clock went back, takes the first occurrence.

Expressions in these slots

A slot’s accepted form is decided before type inference, so the three spellings are not interchangeable:

• a literal is parsed against the grammars above;
• a $: expression must infer to a number, and is therefore milliseconds;
• a ${ } interpolation is refused by name, because it produces a string.

    action: {type: delay, for: "$: input.wait_ms"}   # a number of milliseconds

A target already in the past

Resolution never fails on one — timers keep running while an instance is paused, so a past target is a legitimate state to resume into. What happens next depends on who was waiting:

Slot	Behaviour
a delay	clamps to now and wakes
an external task’s timeout	clamps to now and raises external.timeout
a fetch timeout	refuses — reporting http.timeout for a request that was never sent would be a lie

until is external-only as a timeout. A fetch’s budget is for, and a retry gets a fresh one.