calendar excell not visible within tabbar group

We’re trying to use the calendar excell in a grid which is being displayed inside a tabbar group. The problem is that the calendar simply does not display. There are no javascript errors, as far as we can tell the container div is being populated, it’s just not visible.

The most probably calendar’s default z-Index too low, and it covered by some other container on page.
You can adjust z-index of calendar in next way

    in js/calendar/calendar_init.js locate next string
           this._myCont.zIndex=“19”;

    you can increase this parameter to some bigger value