Time representations

[wpbonelli]

We currently use the builtin datetime.datetime for type hinting component fields and implementing converters.

The one exception at the moment is in the utilities we've already rehomed from imod-python, e.g. the head and budget file readers in https://github.com/modflowpy/pyphoenix-project/tree/develop/flopy4/mf6/utils.

We may need some utilities like imod-python's for more flexible handling of dates/times and converting between representations. Ideally we can be lenient in what we accept, then convert internally into a consistent representation.

Relevant reading

• https://docs.xarray.dev/en/stable/user-guide/time-series.html
• https://docs.xarray.dev/en/stable/user-guide/weather-climate.html#cftimeindex
• https://docs.xarray.dev/en/stable/internals/time-coding.html#cf-conventions-time-handling