Producing one month of data results in QC err

I was producing one month of data for faster iteration during development and got this QC error:
```
[
{
"mip_table": "atmos@mon",
"checker": "Filename and size checker",
"error_message": "197801 is not earlier than 197801",
"affected_files": 1,
"affected_vars": "ztp_tavg-u-hxy-u"
}
]

```

Low priority as users are unlikely to want to produce such a small range of output.

Reproduce the issue by producing one month of data and start from the QC output for the "Filename and size checker" on the atmos@mon table. Trace where the date comparison reports that 197801 is not earlier than itself; done means the one-month output completes QC without this error.

Written by the indexing model from the issue text.