Use datepicker on additional fields on Event#edit

* Previous selector was incorrect, datepicker wasn't working

https://trello.com/c/p6qYU2HJ
* Previous selector was incorrect, datepicker wasn't working

https://trello.com/c/p6qYU2HJ
* Previous selector was incorrect, datepicker wasn't working

https://trello.com/c/p6qYU2HJ
* Previous selector was incorrect, datepicker wasn't working

https://trello.com/c/p6qYU2HJ
* Previous selector was incorrect, datepicker wasn't working

https://trello.com/c/p6qYU2HJ
* Previous selector was incorrect, datepicker wasn't working

https://trello.com/c/p6qYU2HJ
* Previous selector was incorrect, datepicker wasn't working

https://trello.com/c/p6qYU2HJ
* Previous selector was incorrect, datepicker wasn't working

https://trello.com/c/p6qYU2HJ