Complex sentence: In previous years, B101 had gone all-Christmas for 36 hours--from noon Christmas Eve to midnight on December 25--but the extended all-Christmas format proved very successful for Sunny 104.5, which prompted B101 to do the same in 2003.
Split into simpler sentences: In previous years, B101 had gone all-Christmas for 36 hours from noon Christmas Eve to midnight on December 25th. The extended all-Christmas format proved very successful for Sunny 104.5, which prompted B101 to do the same in 2003.