Complex sentence: On January 4,2010, Mark Hoppus began posting via Twitter about a new musical endeavor, at the time entitled 10HRSattheMACHINE.
Split into simpler sentences: On January 4,2010, Mark Hoppus initiated the first announcement of the band. He began posting via Twitter about a new musical endeavor, at the time entitled 10HRSattheMACHINE.