Grafana date format yyyymmddhhmmss

Hi all,
I am testing an upgrade of my environment from elastic 5.2 and grafana 4.5 to elastic 7.6 and grafana 6.6 . ( I cannot upgrade to grafana 7.x for now)

My problem is this: on an index I have a custom timestamp field in the format yyyymmddhhmmssZ, in the old grafana it was perfectly interpreted and time order and date were correct, now it seems not recognize this format giving me and invalid date error. So I changed my application to remove the “Z” at the end, and at this point grafana took it as a epoch millis giving me year 2610, still clearly incorrect.
Why this change has happened? What formats do I have to use? What else can I do? Because to reindex all data could be a problem.
thanks a lot.

I’ve discovered Grafana correctly interprets the yyyymmdd’T’hhmmssZ format so I just had to add a T.