time

Look up time.interval, time.wait, time.now, and time.format, the timers and the clock of an Arc automation.

The time module has timers and the clock. Import it with import time. interval and wait are flow functions: a function body cannot call them.

The period and duration parameters have the type i64 ns. They take a literal, such as 500ms or 10hz, or a variable of type i64 ns. A variable declared as hold := 5s has the type i64 s, and gives error ARC3002 expected i64 ns, got i64 s. Declare it with the type:

import time

hold i64 ns := 5s

sequence fire {
    time.wait(duration=hold) => next
    1 -> ign_cmd
}

true => fire

A literal of 0 or less is a compile error, such as period must be positive, got 0s. A variable that becomes 0 or less stops the timer and reports an error. On the Core the error is a warning. On a Driver it stops the automation.

format

Prints a timestamp as text, in UTC or a time zone.

inputi64 ns* Required

The timestamp to print.

formatstr = ""

The format of the text, from the codes below. An empty format gives ISO 8601, such as 2026-03-07T15:04:05.25Z.

tzstr = ""

The time zone, such as America/Denver. Defaults to UTC.

• Trigger -> optional. Each new trigger runs it, whatever the value. With no trigger, it runs when input has a new value.
• Output -> the text, as a str.
• Function form -> time.format(input, format, tz) str.

import time

true => time.format(time.now(), "%Y-%m-%d %H:%M:%S %Z", "America/Denver") -> start_msg

interval

Fires again and again, once each period.

periodi64 ns* Required

The time between two fires.

• Trigger -> optional. The first trigger starts the timer, and later values have no effect. With no trigger, the timer starts when its stage starts.
• Output -> u8 value 1 on each fire, with the time of the cycle.
• Runs -> on the first timer cycle after the timer starts, then on a fixed schedule, once each period. A late fire does not move the next one. When a cycle takes longer than period, the timer fires once and does not make up the fires that it missed. At the top level, it fires when the automation starts.

import time

time.interval(period=1s) -> heartbeat

now

Gives the current time.

• Trigger -> optional. Each new trigger runs it, whatever the value. With no trigger, it runs once each time its stage starts.
• Output -> the time as a timestamp, type i64 ns. Write it to a timestamp channel or an i64 channel. Another channel type, such as f64, is an error.
• Function form -> time.now(). All calls in the same cycle give the same time.

now has no parameters.

import time

true => time.now() -> start_time

wait

Fires once, after duration.

durationi64 ns* Required

The time to wait.

• Trigger -> optional. The first trigger starts the timer, and later values have no effect. With no trigger, the timer starts when its stage starts.
• Output -> u8 value 1, once, with the time of the cycle.
• Runs -> when duration has passed since the timer started. It counts from zero again each time its stage starts. As a sequence step, the sequence moves on when it fires.

import time

sequence fire {
    1 -> ign_cmd
    time.wait(duration=2s) => next
    1 -> press_vlv_cmd
}

true => fire

The timers follow the same rules on the Core and on a Driver. They never fire early. How soon after its deadline a timer fires depends on where the automation runs and its performance level. See Arc timing.