Big Day, originally titled A Day in the Life, is an American television sitcom that first aired on ABC from November 28, 2006, to January 30, 2007. The series was co-produced by Josh Goldsmith and Cathy Yuspa and directed by Michael Spiller for Sony Pictures Television.

Originally, it was supposed to debut on October 5, 2006, along with Notes from the Underbelly, but ABC made a last-minute change in its schedule by moving Ugly Betty to Thursday, thus replacing both sitcoms whose "buzz" was not especially promising.

Big Day was broadcast on Tuesdays at 9:00/8:00c. The timeslot was to be filled by another new sitcom that had a better "buzz," The Knights of Prosperity, but ABC moved that program to Wednesdays to make Big Day a priority. According to the ratings, Big Day turned out to be a ratings disappointment.When Big Day ended its first season on January 30, 2007, only 12 of the 13 produced episodes aired leaving the 13th episode, titled The $10,000 Check, unaired.

On May 15, 2007, ABC officially cancelled the show after the network announced their 2007–2008 fall schedule.