Why have there recently been several changes in NFL playoff schedules with no reason given?

Last year, the Super Bowl was changed from 5:30 (CST) (It was at 5:30 in previous years.) to five. Also this year in the Divisional Playoffs, the Saturday 7:00 game and the Sunday 3:30 game have been moved to 7:15 and 3:45. This is the change that seems quite strange to me because if the schedule-makers thought that perhaps the early games on those days would last longer than three-and-a-half hours, then wouldn't they have moved the second Conference Championship from 5:30 to 5:45, especially since Conference Championships typically last longer than Divisional Playoffs?