The following page attempts to piece together an approximate timeline for the Between Failures webcomic.
Strip 1 to 304: Monday 19th March, 2007
For the purposes of the Wiki, we assume that Between Failures started on the day of its first strip. Checking back indicates this was a Monday, which would appear consistent with Ed starting his job on a weekday. Thomas also mentions it being chilly outside, which would be consistent with March.
No changes occur during these strips to suggest the timeline has advanced, and the character's outfits remain consistent.
Strip 305 onward