ElasticSearch Index pattern with wildcard and date

Hi,
I’m trying to setup an elasticSearch datasource; failing on the time field. My index pattern looks something like:

backups-{envname}-[201812]

Where envname should be a wild card. I can’t get it to recognise my date field.
With typical beats patterns like

metricbeat-6.4.2-2018.12.07

It works by setting [metricbeat-6.4.2-]YYYY.MM.DD

My date field is called ‘date’ and is def. a date-type field in ES. I guess i need a pattern like:
[backups-*][YYYYMM]

but that and various other combo’s don’t work - i keep getting ‘no date field named date found’. Any ideas?

Ok nevermind, I just set backups-* as the pattern and it’s fine.