You could construct datetimes from those separate vectors of year/month/day, and then plot the datetime variables. That brings you back to 2D and should make things easier to see given the density of your data.
% Cook up some data
>> f.Day = randi(31,10,1);
>> f.Month = randi(12,10,1);
>> f.Year = 2020 + randi(10,10,1);
>> s.Day = randi(31,10,1);
>> s.Month = randi(12,10,1);
>> s.Year = 2015 + randi(10,10,1);
fdatetime = datetime(f.Year,f.Month,f.Day)
sdatetime = datetime(s.Year,s.Month,s.Day)
plot(sdatetime,fdatetime)
