Community property allocation for the first year

My partner and I are going to register as domestic partners In California later this year. We aren’t married to each other so we will file Federal tax return as singles and State tax as RDPs (same as married).

 

For Federal tax return, we need to split our community income since CA is a community property state. If we get married in December, does that mean we only split the income earned in December, and treat income from January to November as separate property?