You may have a good reason for wanting to split up the data, but often it is not necessary, tools like findgroups/splitapply, varfun/rowfun, and groupsummary/etc. let you do things to each day's data sepearately, all at once.
To answer your question, though, I would think you'd load the mat files, vertcat the timetables, and use sortrows. But your description is not really clear to me.
