Complex sentence: They originally planned to switch to this format full time except for Sunday mornings, but initially would run this format from 6 a.m. to 7 p.m. weekdays and 10 a.m. to Midnight Saturdays and not at all on Sundays.
Split into simpler sentences: They originally planned to switch to this format full time except for Sunday mornings. But initially would run this format from 6 a.m. to 7 p.m. weekdays and 10 a.m. to Midnight Saturdays and not at all on Sundays.