It is mentioned by Shane that it is November 19th, Sunday back home. While this was true in 1995 when this episode aired, and in fact it aired on Sunday November 19th. However, in 2063, when this episode is set, November 19th will be a Monday.
In order to breach the enemy bomber, the humans need to blow a hole in the craft, which is apparently replaced later with a Earth-type space hatch system. The Chigs never seem to scan/notice this when the same craft, piloted by humans, tries to breach their perimeter.