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A while ago I created a form using datepicker (fields: Start and Ende): http://digitalfotografieren.com/event-melden/
However, now datepicker is not working/showing up anymore. When I am changing Wordpress to the standard theme, the calendar is working. With my current theme datepicker was also working but I don't know when it stopped showing up (maybe related to WP 3.5 update?). Do you have any idea?
I also disabled every plugin without success.
This is not really a problem with the datepicker. You're loading a really old version of jquery and that's about it.
Please don't post issues if the plugin works with WordPress official themes (twenty*), it's usually the theme that breaks things and there's nothing I can do about that.