January 6th (3 USC Section 15) is an arbitrary date to COUNT the votes.

Congress can change that date, however impractical at this point unless a law exists under some condition that allows it to be changed under "emergency" declaration of some sort...using the Pandemic strategy playbook.

https://crsreports.congress.gov/product/pdf/IF/IF11641

January 6, 2021: Joint Session of Congress to Count Electoral Votes and Declare Election Results Meets On January 6, or another date set by law, the Senate and House of Representatives assemble at 1:00 p.m. in a joint session at the Capitol, in the House chamber, to count the electoral votes and declare the results(3 U.S.C. §15). The Vice President presides as President of the Senate. The Vice President opens the certificates and presents them to four tellers, two from each chamber. The tellers read and make a list of the returns. When the votes have been ascertained and counted, the tellers transmit them to the Vice President. If one of the tickets has received a majority of 270 or more electoral votes, the Vice President announces the results, which “shall be deemed a sufficient declaration of the persons, if any, elected President and Vice President.”