semiatic

On/off timer (clock)

Starts or stops the unit automatically after a delay or at a clock time you set.

What pressing it does

Midea counts in hours from now: each press adds 30 minutes up to 10 hours, then 1 hour up to 24. Mitsubishi Electric and Panasonic set a clock time instead (the clock must be set first), and Panasonic repeats the timer daily. Setting both gives an on-then-off or off-then-on programme.

What it does not do

It does not survive every power cut: Mitsubishi Electric says a power failure cancels the ON/OFF timer, and Fujitsu’s TIMER lamp flashes to ask you to set it again.

Makes differ, check your unit’s manual: the same drawing can mean different things on different brands, and only your model’s manual says exactly what a button does and which modes it works in.

What it looks like
A clock face, often with the word ON or OFF beside or under it; a lit clock lamp on the indoor unit while a timer is set.
Names makers use
TIMER ON / TIMER OFF (Midea); ON TIMER / OFF TIMER (Mitsubishi Electric, Fujitsu); Timed on / Timed off (Samsung)

Where makers differ

Countdown (Midea, Samsung) versus clock time (Mitsubishi Electric, Panasonic, Fujitsu). The oven timer on this site is a different symbol: it times cooking, not the air conditioner.

Other symbols with the same shapes

Sources

No single published standard defines air-conditioner remote icons, so this meaning is taken from 4 makers’ own manuals, each fetched and read on the date shown:

Written in our own words; quotations are the makers’ wording.