We can add user-wise restrictions in the date field through Permissions management and date range function as mentioned below. 

For instance, to prevent a person from making backdated entries in the "Purchase Requisition" form beyond a week, add the folowing conditions in Permissions Management. 

The function you need to use is "daterange(datefieldid,startday,endday);" 

Consider daterange(5001,today-7,today);

In this case 5001 is the date field of Purchase Requisition form

Start day is today - 7 i.e. from today it will allow backdated entries up to 7 days

End day is today i.e. till today it will allow users to make entries

You have to use this function for a particular user for whom you want to restrict the entry and as per the form states i.e. "Draft", "Approval" etc.