You work to a 13 week roster so you know what you’re working and when your rest days are. Some instances of work are allocated as time bands. Band A; 0000-0600, B; 0600-1200, C;1200-1800 and D;1800-0000. If for example you were band D on Monday-Friday you could book on anytime between 1800 and 0000. Once every 13 weeks you get a flex week where you could be allocated 5 instances of work out of 7 which is the worst part of the roster.