Convert a String to a Number / Integer

Hello All,

I am currently working with expression builder, and we want to know what day of the month we are in.

To do so we use : ToChar([<StartCloseDate>],'DD')*1.0

It works well. For october 13th 2014 it returns only 13. The problem is that it convert the date to a string and doing so it is impossible to compute this number.

Is there a way to convert a string in a number ?

Or if not, is it possible somehow to know (using Julian formulas) which day of the month are we in ?

Thank you for any advices.