They offer rosters off as part-time.
The year consists of 13 rosters of 28 days. Pilots can bid for one roster off, two rosters off etc up to 50% part time. Goes with seniority or special needs.
If you get approved two rosters of, two of your rosters during the year will be blank. The salary throughout the year will then be 84,6%. You loose the per-diem when you don't fly obviously.