5-4-4 Last Calender Day change

Hi SAP experts,

currently we are using 5-4-4 calender, as per client requirement we are going to change last calender day.

please suggest impact analysis on this and are there oss notes to be applied? what testing needs to be done?

Month      Day     Period     Year Shift

     2          2          1               0

     3          2          2               0

     3          30         3              0

     5          4          4               0

     6          4          5               0    

     6          28        6               0

     8          3          7               0

     8          31         8              0

     9          28         9              0

     11         2        10             0

     11         28      11             0

     12         31      12             0

thanks

shiva