Fix parsing of timestamps in CF-compliant files produced by CDO.

[JohnHalleyGotway]

Describe the Enhancement

Running the cdo tool using the -import_binary option to read GraDS data produces a CF-compliant NetCDF output file. However the MET tools are not able to parse the timestamps used therein.

Here is an example:

cdo -f nc import_binary 20190710H1radar.ctl 20190710H1radar.nc
plot_data_plane 20190710H1radar.nc r_lev_7000.ps 'name="r"; level="(0,14,,)";'

Only issue is this warning message:
WARNING: parse_cf_time_string() -> unexpected NetCDF CF convention time unit "hours since 1-1-1 00:00:00"

I ran the date command to double-check that the math is correct:

date -ud '0001-01-01 UTC '17694048' hours' +%Y%m%d%H
2019071300

We just need to enable the year, month, and day to accept values of 1.

Time Estimate

2 hours.

Sub-Issues

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Relevant Deadlines

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Funding Source

This is needed for the HAFS METplus use-case to enable MET to handle the output from cdo.
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Define Related Issue(s)

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• METplus, MET, METdb, METviewer, METexpress, METcalcpy, METplotpy
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