"What is considered our official moving date? "
The date you crossed the state line for the last time, with no intention of returning to the old house as your "PRIMARY" residence.
You will most likely be filing a full-year resident return for the old state for the 2019 tax year, since you lived in that old state as your primary residence for more than half the year, and all of your 2018 income is from that old state.
