When/how is a Roth conversion valued?

If I do a Roth conversion between Fidelity accounts of a given number of shares of a Fidelity mutual fund, my understanding is that those shares are transferred in-kind immediately. But when/how is the value of that conversion established, which will be reported on a 1099-R? The mutual fund is priced every evening after market closes, and I expect that the answer depends on what time of the day/night the conversion order is placed.