Move to a previous or following month by clicking the small black triangles in the upper left respectively upper right corner. (Note: if a triangle is coloured grey, the boundary of the valid period has been reached, and no earlier / later date can be selected. In this example, the valid period consists of the dates within the simulation period.)
Since timeseries can be quite long, it might be desired to move a bit quicker through the dates. This can be achieved by clicking the header of the datetimepicker (January, 1981 in the above example). Instead of showing the days within a month, the datetimepicker now shows the months within a year. This can be repeated up till the level where the datetimepicker shows the decades within a century. (Note that the datetimepicker only shows the dates within the simulation interval, and therefore only two decades.)