Access is the first thing an event changes
On a major event day the ordinary approach to a building may be closed, parking is generally unavailable, traffic management may prevent a vehicle reaching the premises at all, and pedestrian routes are redirected. None of that has anything to do with the cleaning work, and all of it determines whether the attendance can happen at the scheduled hour.
Moving the time rather than the route is usually the answer. An attendance well before the build-up begins, or well after the crowd has dispersed, avoids the restriction entirely. Because the dates are published a long way ahead, that adjustment can be rostered as part of the normal plan rather than arranged at short notice when everybody in the precinct is doing the same.
