332mistress - Complicated is the right word! My understanding of the working time directive view on leave, is that a weeks leave should entitle the worker to one week away from work. Thus a weeks leave for a 5 day/week worker would equate to 5 days while a 3 day/week worker would equate to 3 days leave. The minimum requirement of the directive is 4 weeks leave per year so your 'standard 5 day a week office worker' requires a minimum of 20 days leave per year.
If you work on the basis that someone on an equal time on/off roster works a 3 1/2 day week, this would equate to only 14 days leave per year. However, and it is a big however, an offshore equal time on/off roster is not in reality equal time on/off, due to the change over flights, positioning etc. Additionally, I do not believe any major operator offers the minimum leave required by the directive.
Balancing this, is the fact that a two weeks on/two weeks off roster with two weeks leave is in fact a damned good deal when you look at it and compare with other rosters.
I realise I have sat happily on the fence and argued both sides of the discussion but then as you said, it is complicated!!
Cheers
TeeS