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