Yeah the OBCs don’t need to be regrided vertically - MOM6 does this online thankfully so you don’t have to have extra big boundary files to match your model’s (presumably finer) vertical grid.
Regarding the time dimension: the boundary class does have the option to specify the time units of the boundaries, however this hasn’t been implemented in the wrapper method setup_ocean_state_boundaries which we use in the demo.
For context, users used to have to call the segment class for each segment (and still do if they want to do more complex things with their boundaries). But we decided to wrap this up in one function to keep the demo notebook streamlined and easier for beginners. But clearly we forgot to include some edge cases! An easy fix is just to add a key word argument to the ocean state boundaries function, which passes the time units onto the boundary segment class on initialisation.
@Lizzie would you have time to do this as a quick PR?
To fix the data you’ve already made, you just need to modify the metadata to correct the time units. At the end of the day that’s all that rmom6 does: writes the appropriate time encoding into the netcdf file before saving it.