hemerology
The study of calendars, especially with a view to identifying propitious days.
countable, uncountable
Hemerology, (Greek) a Calender, or Book, wherein are regiſtred the paſſages of every day.
Where it comes from
From Ancient Greek ἡμέρᾱ (hēmérā, “day; date”) (a variant of ἦμαρ (êmar, “day”), ultimately from Proto-Indo-European *h₂eh₃- (“be hot, burn”)) + -ology (from Ancient Greek -λογῐ́ᾱ (-logĭ́ā, suffix indicating the study of something, or a branch of knowledge), from λόγος (lógos, “word; explanation; subject matter”) (from λέγω (légō, “to arrange, put in order”), from Proto-Indo-European *leǵ- (“to gather”)) + -ίᾱ (-íā, suffix forming a feminine abstract noun) (ultimately from Proto-Indo-European *-i-eh₂ (suffix forming a collective noun))).
Adapted from the Wiktionary entry hemerology (CC BY-SA 4.0).