In which period should I reverse the revaluation journal of December?

Hello,

My client is in the end-year closing process. In this company the revaluation is run once per year, in December. It has an accounting calendar of 14 periods (12 periods + 2 Adjustment periods, one is in the beginning and the second is in the end after December). In which period should he reverse the revaluation journal of December?

He entered as Unrealised gain/loss account (in the revaluation form) an expense/revenue account and since it is the end-year closing the balances of this accounts will go automatically in the retained earning account and now my question is  ‘What will happen with the account balances of the Unrealised gain/loss account when the revaluation journal will be reversed in the following period? Because as I mentioned the balances of this accounts will be already transferred in retained earning account when he opens the next year.