Convert string variable to date to be able to use DaysBetween function

I have a user string variable that returns a date string with format dd MMM yyyy 01 JAN 2014 or 1 JAN 2014 in some instances. I need to be able to format this as a date variable so I can calculate the number of days between two dates. My other variable is a date variable that returns 01/01/14 (dd/mm/yy). I have used ToDate formula to try to convert the string to date but it returns an #ERROR. I need suggestions on how to be able to convert the string to a date format.

Thanks!