Basic date Regular Expressions

1. "dd/mm/yyyy","(3[01]|[12][0-9]|0[1-9])/(0[1-9]|1[012])/[1-2][0-9][0-9][0-9]"
2. "dd-mmm-yy","(3[01]|[12][0-9]|0[1-9])[-/][a-zA-Z][a-zA-Z][a-zA-Z][-/][1-2][0-9][0-9][0-9]"
3. "MM/dd/yyyy","(0[1-9]|1[012])/(3[01]|[12][0-9]|0[1-9])/[1-2][0-9][0-9][0-9]"
4. "yyyy-mm-dd","[1-2][0-9][0-9][0-9][-/](0[1-9]|1[012])[-/](3[01]|[12][0-9]|0[1-9])"  
5. "yyyy/mm/dd","[1-2][0-9][0-9][0-9]/(0[1-9]|1[012])/(3[01]|[12][0-9]|0[1-9])" 

I cheated on MMM , I know