DayPilotCalendar itself has no z-index specified (only certain objects, like the moving shadow and the bubble).
You can try the following:
- Put DayPilotCalendar inside a <div> element with z-index specified.
- Render your date picker after DayPilot - i.e. have DayPilotCalendar before the date picker in the .aspx file (you would have to arrange the visual order using positioned <div> elements).
However, it's strange that iframe renders behind DayPilotCalendar. There is a known bug of IE (
ie z-index bug) and one of the workarounds uses
iframe to fix it.