Vespers Rubric

The word “vespers” comes from the Greek ἑσπέρα (“hespera”) and the Latin vesper, meaning “evening”.
Vespers opens a Church day, so it relates to the next day of a week, eg. Saturday afternoon a Sunday’s vespers is served.

Period of Octoechos*
from Monday after the All Saints Day to the (Lenten) Triodion

*from the Greek: ἡ Ὀκτώηχος [okˈtoixos]; from ὀκτώ “eight” and ἦχος “sound, mode” called echos