cyclic forcing with a daily forcing dataset requires offset = -1

[mnlevy1981]

We want to spin up the CESM-forced runs by repeating a single year of forcing with day_offset = -0.5 (because POP provides the date as the end of the averaging interval instead of the middle), but if I don't set day_offset = -1 then biomass is NaN globally / for every functional type after the first time step.

I think something weird is happening when we try to prepend the last day in the forcing dataset to the beginning (changing the date to Dec 31, 0000), but I haven't dug deep enough to know exactly what is going wrong