irregular work hours; shift work
Refers to work schedules that deviate from a standard fixed pattern, including rotating shifts, split shifts, or non-standard hours.
This factory has introduced irregular work shifts.
Because of the irregular work hours, my daily rhythm tends to become irregular.
シフト勤務 specifically refers to shift-based work with rotating schedules, while 変則勤務 is broader and includes any non-standard work pattern.
不規則勤務 emphasizes the irregularity of the schedule, often with a negative nuance, whereas 変則勤務 is a more neutral term for non-standard arrangements.
Compound of 変則 (irregular, anomalous) and 勤務 (work, duty). The exact historical derivation is uncertain, but the term is a straightforward modern compound.