What kinda GM was this?

[Catapult]

I can't find any evidence of a day of the week through the calendar system displayed in-game? How do people know there are 8 days a week?

In the arcanist, thaumaturge's and conjurer's guilds there are a collection of "dusty tomes" that talk about the elements, time and ages. They describe the cycle of ice>water>wind>lightning>fire>earth. This cycle combined with astral and umbral make the set of 8 days in a week. Four sets of this cycle create a month of 32 days.

The months themselves also follow a cycle of astral and umbral elements. The seventh moon is the astral lightning moon, which is represented by Byregot the builder. I'm not sure if this protends to anything.