It is Unification Day fellow Browncoats! You know what to do.

Unification Day was the day when the Unification War between the Union of Allied Planets and Independents ended and the outer planets came under the control of the Alliance. It is celebrated yearly by pro-Alliance citizens throughout the 'Verse. Some former Browncoats, Malcolm Reynolds for example, do their best to rain on the parade; in his case by essentially picking a fight in a different pro-Alliance bar each year.

A similiar holiday was Alliance Day. November 20