rework check_group_daterange to work with data starting at year 0001

[jtmims]

Description
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Checklist:

• My branch is up-to-date with the NOAA-GFDL main branch, and all merge conflicts are resolved
• The scripts are written in Python 3.12 or above (preferred; required if funded by a CPO grant), NCL, or R
• All of my scripts are in the diagnostics/[POD short name] subdirectory, and include a main_driver script, template html, and settings.jsonc file
• I have made corresponding changes to the documentation in the POD's doc/ subdirectory
• I have requested that the framework developers add packages required by my POD to the python3, NCL, or R environment yaml file if necessary, and my environment builds with conda_env_setup.sh
• I have added any necessary data to input_data/obs_data/[pod short name] and/or input_data/model/[pod short name]
• My code is portable; it uses MDTF environment variables, and does not contain hard-coded file or directory paths
• I have provided the code to generate digested data files from raw data files
• Each digested data file generated by the script contains numerical data (no figures), and is 3 GB or less in size
• I have included copies of the figures generated by the POD in the pull request
• The repository contains no extra test scripts or data files

[wrongkindofdoctor]

you can replace multiple characters in one call without having to explicitly check for them, e.g.,

time_vals[i] = time_vals[i].replace('-', ':').replace('', '').

[jtmims]

I'll condense that for the final PR