十三日

十 = 一 + 丨 : Mnemonic symbol: a holy cross. Sherlock Holmes (sh-) is investigating a very strange thing he found in the kitchen of the space station (-2): A big pyramid made of ten (十) crosses (十), which are in turn made out of flutes (一) and dinosaur bones (丨).

三 = 一 + 二 : Mnemonic symbol: a Cartesian coordinate system with three (三) axes.

Socrates (s-) is performing in front of the anthill (-an1). He created an electrical flute by attaching a large capacitor (二) to the flute (一), so that he can get the attention of all the ants. Moreover, he's balancing on a Cartesian coordinate system (三). Unfortunately, only three (三) ants stop to watch the performance.

日 = 囗 + 一 : Robinson Crusoe (r) is hiding from the sun (日) in an enclosure (囗) full of flutes (一) in the space station's bathroom (Ø4).