With that convoluted title I’m making myself think about what we’d call the additional days on other planets or other different temporal circumstances.
Instead of ending them with -day you could end them with the planetary body name or circumstance name. Today might be Lajove on Jupiter!
Nice a Jupiter day or a Lajove is only 10 Earth hours. Mercury on the other hand is over 1000 Earth hours. https://spaceplace.nasa.gov/days/en/