I think it will be much better if validation of work can be applied not only for the current week but to all backward work.

I understand the resquest, as this function came late for existing project, but I don't share this point of view.
It's really a mess to validated something that is not displayed on the current screen.

Another point: we have occasionally people who is booking their work by mistake into year forward. Can it be implemented some kind of parameter to pop-up warning if date is too far forward (set by this parameter)?

Request recorded as Ticket #1054