Use of DateTimeFormatter#ISO_OFFSET_DATE_TIME drops millis when they're zero.
So the formatted date could be "2011-12-03T10:15:30+01:00" (millis to 0) or "2011-12-03T10:15:30.354+01:00" (millis > 0)

Possible fix : use of DateTimeFormatter.ofPattern
http://stackoverflow.com/questions/35184481/java-8-datetimeformatter-dropping-millis-when-theyre-zero