I am using dynamics sl web apps 2015 cu2 and when I open the latest timecard (the current one), I get this error: 

the added or subtracted value results in an un-representable DateTime

and it is pointing to this: Line 137: Dim TimeSpan As TimeSpan = New TimeSpan((ProjectTimecardUIHelper.GetPeriodDays(Model.EndingDate, Model.EndingDate).Count() - iDate - 1), 0, 0, 0)

Note that all previous timecards open fine, it is just the latest one with current date. Also it is not a future date. when I add another period in the week maintenance, then the error moves to the latest week. Any Idea?