The income from the IRA should be apportioned to where the income was received.
If you received equal monthly payments, then you would allocate 8 payments to Utah and 4 payments to California.
If you received a single lump sum payment, you should allocate that income to the state you were living in at the time of the payment.
Or in other words, any payments you received at any time would be allocated on the income tax for the state you were living in at the time of payment.
