When do missionary charges hit the ward account?

Is there a set date when missionary charges hit the ward account? I generally see them the first week and was curious if there was an actual date. Also, are charges for the current month or the previous month? For example, a charge hits on Nov 2. Does that charge get applied to Nov or Oct?

It's usually during the first week but based on past history there isn't a set date. Looking back over this year it has varied from the 2nd to the 6th of the month. Charges are for the previous month (this has changed in the last year or so--it used to be for the month when the charge was made).