Londo is in late season 4, as is G'Kar. Vir is either also late season 4, or writing as Emperor Cotto post-show (those entries are marked as such). Sheridan is early season 4 or late season 3, except when interacting with L, G & V. Garibaldi, however, is season 1 because the writer obviously is a huge Garibaldi/Sinclair'shipper and didn't want to write later G. So she had him fall through a time hole and switch places with his older self.

Oh, and stark is season 3 FS, which you probably will have noticed.*g*