End of year accounting

[Javan Bowsher]

If I have a guest stay for a week, starting in December and leaving January 1, how should I account for the revenue from that stay, as it is in the transition from one year to the next? Would all of the revenue go into January's revenue, all into December's, or should I average the stay and put 6 nights of revenue into December and 1 night into January?

Thank you!