Find the MONTH in a range when we're provided the entire date

Someone threw us a curveball.

This formula was working perfectly

=IFERROR(LOOKUP(2,1/((OrderIDs=K28)*(IO_Months=E30)),ROW(IO_Months)),0)

Now we're told that instead of being given the text name of a month, we'll be given an entire numerical date but still have to extract the MONTH info.

How can the existing formula be modified?

NOTES
IO_Months is a named range on a raw data sheet
Cell E30 (on the main page) currently says "January"
Cell E31 says "February" ...

So, the IO_Months range will stop having "January" and will start showing, for example, "1/19/12"
I was looking for a way to nest the MONTH function in here and haven't figured it out.

Thanks for your help!