=SUMPRODUCT((Data!$K$2:$K$500>=E3)*(Data!$K$2:$K$500<=E4))

Formula above shows range of cells with dates in (K2-K500 in tab called Data) and then E3 and E4 are start and end dates.

E3 = 01/11/2015
E4 = 30/11/2015


However the total returned is not including those cells that have 30/11/15. The cells that contain the dates also have time stamps on them (eg 30/11/2015 10:48:08) so I assume the time stamp is doing something to scewiff the data. Can I do anything in the formula or in the cells that contain the start/end dates to incorporate time stamps or should i just amend the end date to 01/12/15?

Thank you.