In its broadest sense, any period of work that covers mid-night. However, depending upon the context and the type of shift system used, it means slightly different things. Some of the main usages are.
- Daily hours worked by permanent night shift workers, whatever their duration.
- In systems based on two (12hr) shifts a day. The shift that covers the period either side of mid-night. Frequently 18.00 to 06.00 or 19.00 to 07.00.
- In systems based on three (8hr) shifts a day. The shift that incorporates mid-night. For example 22.00 to 06.00.
- In continuous systems with an integrated Night shift. The period of double cover.