Time Coordinate Detection Failure when multiple numpy.datetime64 with units exist in the variables.

[david-sh-csiro]

Using dataset.ems.time_coordinate on some datasets yields an unexpected time coordinate.

When multiple numpy.datetime64 that have units exist within the dataset variables, the logic for looking up time coordinates can pick the unexpected one.

For the below dataset, it will find the 'forecast_reference_time' as the time coordinate variable instead of 'time'.

Excerpt of the dataset.

        int64 forecast_reference_time(time) ;
                forecast_reference_time:units = "seconds since 2024-02-28 00:00:00" ;
                forecast_reference_time:standard_name = "forecast_reference_time" ;
                forecast_reference_time:calendar = "gregorian" ;
        float sfc_temp(time, lat, lon) ;
                sfc_temp:standard_name = "surface_temperature" ;
                sfc_temp:long_name = "surface temperature" ;
                sfc_temp:units = "degrees C" ;
                sfc_temp:coordinates = "time, lat, lon" ;
        double time(time) ;
                time:axis = "T" ;
                time:bounds = "time_bnds" ;
                time:calendar = "gregorian" ;
                time:long_name = "time" ;
                time:standard_name = "time" ;
                time:units = "days since 1970-01-01 00:00:00 00" ;
                time:coordinate_type = "time" ;

Looking at the source code it appears to prioritise finding the first variable that is a numpy.datatime64 with units over things like the CF convention standard name.