You may wish specify study period limits for temporal and spatio-temporal clustering methods if the data file contains more information than you need, if the data file contains different temporal information for different regions within the study, or if you wish to omit including time periods when case counts are zero.
In the latter case, missing time intervals in the submitted data set will be filled with case counts equal to zero. This approach can be especially useful for spatio-temporal data, in which all regions in the dataset must have the same temporal range.