Every state has the authority to develop their won election laws, without interference, unless they violate the constitution.
An extension of the timeline to count their ballots is wholly within the purview of every state.
“An extension of the timeline to count their ballots is wholly within the purview of every state.”
However, if the election involves the presidential race, then any changes to how that election is run, including extending the timeline for accepting and counting ballots, must come from the legislature, not the courts. The legislature is given sole authority for determining how the electors are chosen, and if a court mandates a change to that process, it would be in violation of the US Constitution. Not just my opinion, but also the thinking of Kavanaugh in his opinion on the Wisconsin case.
“An extension of the timeline to count their ballots is wholly within the purview of every state.”
There is a distinction between counting after the day and voting after the day. The Constitution says Tuesday.