Check to see if one date is equal to another minus 1 day

I have two datasets that I need to check for correlations against each, however the correlation I need to do relies on the data from the previous day in 1 set affecting the data in another set. I need to clean the data so that holidays in one set of data from Europe are not affected by the lack of similar holidays in the US (the other data location). To do this I simply need to ensure that cell B7 is equal to cell E6 - 1 day, however I am not sure how to get this function working. the dates are in a dd/mm/yyyy format currently. Any help would be much appreciated.

Thanks