Complex sentence: On Saturdays the first northbound train leaves at about 6:15 am and the first southbound train leaves at about 6:45 am, with the last northbound train leaving at 10:53 pm and the last southbound train leaving at 11:28 pm.
Split into simpler sentences: On Saturdays the first northbound train leaves at about 6:15 am and the first southbound train leaves at about 6:45 am. The last northbound train leaves at 10:53 pm and the last southbound train leaves at 11:28 pm.