Complex sentence: The particulars for the convention were determined on January 15 and the original deadline for candidates to enter the race was June 23,2005, on July 4 the party announced the deadline had been extended to July 12.
Split into simpler sentences: The particulars for the convention were determined on January 15, and the original deadline for candidates to enter the race was June 23,2005. However, on July 4 the party announced the deadline had been extended to July 12.