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A week in the immaterial plane in which Blaseball takes place has nine days, as revealed in the text for the Observed and Unstable modifications.

The remainder of this article contains lore created collaboratively by the Blaseball community.

The nine days of the week are Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Urnsday, and Nersday. They are named after the Germanic names of the planetary deities (the sun, moon, Tiw, Wotan, Thunr, Frige, Saturn, Uranus, and Nerth, respectively) through interpretatio Germanica.