Automatically sort rows by date
 

I am new at code and need help on automatically sorting.
Automatically sorting from [row 20 down to row 590, columns A:L]
By dates that are in column A 20 thru A 590, after entering data in the row.
I need the entire row to be chronologically sorted.
Note: The rows from 1 to 19 must be left unaltered.
Can someone please help me.