When Garibaldi is talking about his witnessing the Shadow ship on Mars he says that his ship went down and "...two of us had to walk out." The other person was Jeffrey Sinclair, and that was when Garibaldi first met him. He also told part of this story to a reporter in Infection (1994).
The ISN reporter's line "President Clark has signed a decree today declaring martial law" was later one of the phrases featured in the opening sequence of Season Five.
This takes place from March 18 to April 8, 2260.
The tale of the Shadow ship buried on Mars ties in with issues 5-8 of the Babylon 5 comic books.