When you create a warehouse in AX you have the option of assigning a calendar to the warehouse for planning purposes. If you need to specialize the calendar for the warehouse because of the operating times it works then you can assign one to the warehouse. This is a quick walk through of the effect of the calendars with regard planning and in this example ATP.

You will also see in this example how the shipping calendar on the legal entity comes into play here if you wanted a company wide default.

Cheers

Lachlan