We could add that but considering in the rest of the cases, the String format is used, this would not be consistent.
By the way, the reason why longs are not used is because in case of automatic mapping (default), the long will cause a numeric type to be used by ES instead of a date (hence the use of date as String).

currently i cant sink a date to ES, 'cos it throws an exception : so, i would rather have a long auto-map than an exception, because i can at least then get reasonable behaviour with a mapping

do you have a better solution in mind ? i'm mostly unfamiliar with ES codebase, but if it's not too onerous i can do a patch ?

Just pushed a fix for this. Can you try the master - if you want I can kick off a nightly build (it will be another 10-15 min).

np : i can try master...

that seems to be working just fine. awesome ! thank you

would it fail if i had specified a custom format in my mapping though ?

yes it would unfortunately-that's the downside of it. However in practice it is recommended to add the custom date format in addition to the default one (which is ISO 8601).

Thanks for the feedback!