The Mozambican Constitution (art150) says that "the President of the Republic shall be sworn into office by the President of the Constitutional Council in a public ceremony before the deputies of the Assembly of the Republic" (Parliament), which means after the parliament takes office. The Constitutional Council (CC) noted In a statement last week that the Constitution (art 85) requires the first session of parliament  to “take place within 20 days after the proclamation of the election results".

The CC continues that “Taking into consideration the fact that the current legislature took office on 12 January 2020 and that it has (...) a five year duration, we are faced with a temporal condition of a constitutional nature which obliges its strict observation by this body", said the statement.

So if the CC wants to stick with 12 January for the opening of parliament, Monday 23 December is 20 days before 12 January and thus the earliest possible results date. The CC  has announced results on Christmas eve before.

But these dates appear to are flexible. Parliament could open earlier and/or fewer than 20 days after announcement of the results, thus in early January or even late December. One suggestion has been 13 December for the results and an opening of parliament just before or just after Christmas.