Alternatively, simply
xlim([datetime(2019,1,1) datetime(2019,1,31)])
will leave all the data plotted but only display that between the two dates selected for the axis limits. This would let you simply reset those to change the visible portion without replotting each time.
Of course, if you want to look at the data and do something else with it (as almost certainly will if not yet), then groupsummary and rowfun will be your very best friends "realsoonnow™"
