Season 6 Episode 14
Episode aired february 12, 2002
after dawn talks to a guidance counselor about her feeling lonely, she accidentally puts a spell on buffy and her friends, trapping them inside the summer's house with a sword-wielding demon.
this marks the last time that buffy's birthday is celebrated in the series. spike comments that, because supernatural events have a history of occurring on buffy's birthday, she should probably stop celebrating them. buffy traditionally celebrates her birthday around the 12th or 13th episode of each season; her birthday takes place in episode 13 of season two (innocence (1998)), episode 12 of season three (helpless (1999)), episode 12 of season four (a new man (2000)), and episode 13 of season five (blood ties (2001)).