DateDiffDays + Create List Item: SharePoint Calendar Event Bar Too Short!

This may be more of an issue related to SharePoint rather than Nintex, but I'd like to know how best to overcome this using the latter.

Using dateDiffDays to calculate dates in calculated field, whose value is then stored in a column and used to create a calendar list item.

In my example, the start date is 18th and ending on the 22nd but the calendar event bar stops at 21st 00:00 even though its tooltip is showing 22nd.

I even went as far to use dateaddhours (+25 hours) hoping the bar would go over to the 22nd but it still stops on the 21st!

Is there a way to specify the default start time for an all day event in SharePoint? That would pretty much fix my issue.