Green’s Dictionary of Slang

bull’s-eye day n.

[one scores a financial bull’s eye]

(Irish) Wednesday, the day on which British Army pensions are disbursed.

[UK](ref. to 1920s) A. de Courcy in Verdon Shawlies, Echo Boys, the Marsh and the Lanes n.p.: Every Wednesday in Ireland was called Bull’s-Eye Day because that’s when the soldiers got their pensions.