The 538 members of the Electoral College will meet on Monday 14 December 2020, which will be Tuesday 15 December 2020.
They do not meet as one body. They will meet in the 50 state capitals and DC. The times they meet range from 10 am to 3 pm local times. So I’d expect most to be over by midday Tuesday NZDT.
There are 306 electors pledged to Biden and 232 pledged to Trump. It is not uncommon for there to be one or two faithless electors who may not vote for the candidate they are pledged to. In 32 states and DC the law requires an elector to vote for the candidate they are pledged to.
Each elector will write the name of their preferred President and VP on a piece of paper and each state will total up the votes and sign six certificates with the results.
The six copies go to the President of the Senate, the Archivist of the US (2 copies), the state’s Secretary of State (2 copies) and the chief judge of the district court covering the state capital.
Then it is all over, bar the counting of the votes by Congress on 6 Jan.