SP2013 DatePicker iframe is missing height and left in style attribute

Question

I have a Webtemplates Solution based on the PROJECTSITE template and the seattle.master. After deployment all site collections based on my template will be provisioned by powershell in an automated process.

Inside this template I use a Calendar. When adding a new entry by clicking on the ADD link, the form will be opened in a dialog and all looks ok. Now after clicking on the calendar icon to open the DatePicker, the iframe is missing the height and left inside the style attribute. This results in a wrong positioned DatePicker

When I provision a site collection based on my custom template over the SharePoint UI (CA -> Add new site collection), everything works fine. The DatePicker gets the correct height and left information.

The described problem only occurs, when using IE 11. If I open any of these site collections in Chrome, everything works as expected.

Does anyone have any idea, where to look for a solution for my problem? I have searched for a similar problem on the net, but have not found any hint.

Answer 1

After a complete investigation together with a colleague, I have found the issue which causes this error. In our powershell script for provisioning the site collection was a function which adds a javascript to the page header. This js File was only needed to overwrite the "Create new subsite" and caused the error in the calendar lists. After modifiing the js file, to only execute the inside function, if the window.location.href matches the viewlsts.aspx the datepicker works as expected again.