It’s Britney Spears Day, bitch!Caesars Entertainment announced last month that the pop star would be honored with her own holiday on Nov. 5, and it has arrived! Today, Clark County Commission Chairman Steve Sisolak will present the “Circus” singer with her official proclamation and a key to the Las Vegas Strip! The Sin City festivities will officially kick off at the LINQ Promenade at 5:30 p.m. and the first 100 “Britneys” in line will win tickets to Spears’ concert at the Planet Hollywood Resort & Casino, plus a ride aboard the High Roller observation wheel.