I build this regular to check month 30/31 and let february to 29.
new RegExp(/^((0[1-9]|[12][0-9]|3[01])(\/)(0[13578]|1[02]))|((0[1-9]|[12][0-9])(\/)(02))|((0[1-9]|[12][0-9]|3[0])(\/)(0[469]|11))(\/)\d{4}$/)
I think, it's more simple and more flexible and enough full.
Perhaps first part can be contract but I Don't find properly.