datenum(ye​ar,month,d​ay,hr) that returns integer

I need a datenum(year,month,day,hr) that returns an integer, where year, month, day, and hr are vectors of integers.
motivation: I am trying to do this for fast lookup of many dates in a large table, where each row contains data for an hourly sample. Therefor the output of datnum will become the indices of a sparse matrix containing the row indices of the original table of data.