We normally have seven crews (watches) here in the US at large centers. Our normal watch schedule is two evening shifts followed by two day shifts followed by a midnight shift. Where I work it is something like this, Sunday 1430 - 2230, Monday 1330 - 2130, Tuesday - 0630 - 1430, Wednesday 0630 - 1430, Thursday morning - 2230 (Wed) - 0630... It makes you old before your time...
regards
Scott