I've put *a* fix in there by introducing a new wrapper function. Ideally we would just point the C API at the argument clinic-generated function, but because it takes a single positional argument the argument clinic outputs a METH_O function instead of METH_VARARGS.

I think these are the options:

1. Modify the argument clinic spec to force METH_VARARGS for a single positional argument taking an object - if that's possible.
2. Maintain a wrapper function for the C API that just unpacks the tuple and passes it to the date_fromtimestamp function that the argument clinic is *also* wrapping.
3. Revert the argument clinic change and manually manage the date_fromtimestamp function as a METH_VARARGS classmethod.

I don't know enough about the argument clinic to know if #1 is feasible, if it is and someone can point me in the right direction, I can update my PR. If not, I think I mildly prefer #2, since maintaining a thin wrapper that unpacks a tuple is not terribly difficult compared to maintaining the method definition stuff.

Since this was an accidental break in the C API, I've marked it as a release blocker.