clock on vs clock in

clock on and clock in both are verbs.

Word	Noun	Adjective	Verb	Adverb
clock on	No	No	Yes	No
clock in	No	No	Yes	No

As verbs, clock on and clock in are synonyms defined as:

Other synonyms of clock on include punch in.

clock on (verb)	clock in (verb)
register one's arrival at work	register one's arrival at work