As you probably surmised you can't shorten a calendar less than one year but you can definitely import data that has a shortened time frame by using filters and a saved view. The saved view will allow you to create any length of time you wish. So perhaps in your example you would put a filter on the module 1 that filters out anything older than 2018. Then use that saved view to import the data into module 2.
Re: Data Import one model to another with Subset of Time Dimension
@JaredDolich Great suggestion. However I feel Anaplan platform should be enhanced to limit the Months in a year while using Time dimension (I guess enhancing Time Range to include periods and years along with allowing to update Time Range via APIs / Anaplan connect for automation). This would be a great enhancement and game changer and would help in optimizing the models too.