convert ereg to preg - example given

Question

I am getting a Deprecated: Function ereg() is deprecated in an old plugin I am updating. I need to update the following two:

ereg( "([0-9]{1,2})-([0-9]{1,2})-([0-9]{1,4})", $fecha, $mifecha);

ereg( "([0-9]{1,2})/([0-9]{1,2})/([0-9]{1,4})", $fecha, $mifecha);

Can someone help me understand what to change to convert them to preg?