Two separate Excel columns, one is YYYY-MM-DD, the other is HH:MM:SS. Trying to figure out how to convert those two Excel columns in to one MATLAB value.

Like I mentioned in the question, I have two Excel columns with values in the following format: 2012-08-28 and 17:07:44, respectively. I have tried to use xlsread to bring those two columns in to MATLAB, but it does not simply bring that data from the Excel file. I thought maybe I could use datenum, but I haven't had any luck with that either. Ultimately I'd like to have one MATLAB value, taking in to account both of the Excel column values. Any tips or suggestions are greatly appreciated! Thanks!