Dateformat changes in external linked sheets

I've created a table to manage our school-year. Out of this table several calendars should be created. As there is no possibility to create more than one calendar out of one tablesheet I worked with markups and created external links to some other tablesheets so that there is one sheet for every group I have to manage. Unfortunately the dateformat changes from "" in the original table to "mm/dd/yy" in the linked table. The calendar does not publish these dates. How can I have smartsheet to avoid changing the dateformat?