how do change Emp category base on date

Question

i have a table in sql like following structure

Id   Emp_Id       Category_Id
1     sss             A 
2     CCC             A
3     VVV             B
4     BBB             B 

I am using following code to get day from the given date

Hide Copy Code

   Int16 day = Convert.ToInt16(SafeConvert.ToDateTime(txtDate.Text).Day); 

i want that if day is even then change employee with category 'A' Change to category 'B' and Employee with category B CHANGE TO 'A',IF day is odd then opposite happen without changing the original table value that is store in table by user.