langsyne vs old times

langsyne and old times both are nouns.

Word	Noun	Adjective	Verb	Adverb
langsyne	Yes	No	No	Yes
old times	Yes	No	No	No

As nouns, langsyne and old times are synonyms defined as:

Other synonyms of langsyne include auld langsyne, good old days, lang syne.

langsyne (noun)	old times (noun)
past times remembered with nostalgia	past times remembered with nostalgia

langsyne (adverb)	old times (adverb)
of the distant or comparatively distant past