colour highlight with conditional formating for partial dates?

Hello,

as per heat map tab in attached..

I am hoping its possible to use conditional formatting to show when any date (mm/yy and disregard dd) shows up more than twice highlight red? eg:if oct- 14 appears twice highlight red, if nov-14 shows up more than twice hightlight red etc?

Izzy

Use a formula of

=AND(ISNUMBER(E3),COUNTIF($E$3:R$24,E3)>1)