How to sort Date column 56 when = to 55 and formatted to display only month name

My column 55 holds birthdates and formatted as 1-9-12.
My column 56 equals column 55, and is formatted to only show month . . . January etc.

I've tried sorting column 56 and it will not sort this column, as I think that it is caused by using date data from column 55.

I don't want to use a macro if I don't have to.

Any ideas?