dateline vs date-mark

dateline is a noun but date-mark is not a noun.

Word	Noun	Adjective	Verb	Adverb
dateline	Yes	No	Yes	No
date-mark	No	No	Yes	No

As verbs, dateline and date-mark are synonyms defined as:

Other synonyms of dateline include datemark.

dateline (noun)	date-mark (noun)
a line at the beginning of a news article giving the date and place of origin of the news dispatch
an imaginary line on the surface of the earth following (approximately) the 180th meridian

dateline (verb)	date-mark (verb)
mark with a date and place	mark with a date and place