day book vs police blotter

day book and police blotter both are nouns.

Word	Noun	Adjective	Verb	Adverb
day book	Yes	No	No	No
police blotter	Yes	No	No	No

As nouns, day book and police blotter are synonyms defined as:

day book and police blotter: the daily written record of events (as arrests) in a police station

Other synonyms of day book include blotter, charge sheet, rap sheet.

day book (noun)	police blotter (noun)
the daily written record of events (as arrests) in a police station	the daily written record of events (as arrests) in a police station