At FedEx a day starts at 01:30am local base time.

A reserve period A (RP-A) is a 12 hour period of time beginning at the start of the day (01:30). 01:30-13:30

RP-A+ is a 12 hour period of time beginning 6 hours after the start of the day. 07:30-19:30

Reserve Period B (RP-B) is a 12 hour period beginning 12 hours after the start of the day. 13:30-01:30

Reserve Period B+ (RP-B+) is a 12 hour period beginning 18 hours after the start of the day. 19:30-07:30

Reserve Period 24 (RP-24) is a 24 hour period of time beginning at the start of the day.

Reserve pilots on RP-24 must be given a minimum of 24 hours notice prior to showtime. All others are usually 1.5 hours notification prior to showtime.