Time column other than index

As far as I have understood, the index column is a unix epoch written to influxDB as a string.
When selecting Options, Column Styles, Time -> Date, it is possible to select 3 pre-configured data formats and the unix epoch is beautifully changed into a date according to the data format.

Let us now have other columns that contain unix epochs. Unfortunately in that case when I select the column name as “name or regex” and select date Grafana only shows invalid date.
Is this due to the fact that the values need to be a certain string or number format (int, float, long)?
Does the conversion from time/epoch to date maybe only work for the index column?
Is it maybe due to my old version of Grafana (3.1.1)?

I would really like to make these epoch columns visible in a way that makes sense, so where can I find information on the input types?
The documentation says:
Type: The three supported types of types are Number, String and Date.
Format: Specify date format. Only available when Type is set to Date…

But what about the format that data should have in InfluxDB so they can be used as date. Unix epochs would be my favorite.

Testing this in the latest version of Grafana this definitely works. Try changing the value column to Date: