I am facing the same issue.

Currently for my ZonedDateTime the format generated for the date attribute in ES is :

"startDate": {
"format": "yyyy-MM-dd'T'HH:mm:ss.SSSZZ'['ZZZ']'||yyyyyyyyy-MM-dd'T'HH:mm:ss.SSSSSSSSSZZ'['ZZZ']'",
"type": "date"
}

and the TimeZone is mandatory.

Is there a way to change the date format generated for elasticsearch? A simple long would be enough for me.