L L wrote:
The dates are set.
There are no dates.
The president nominates a person.
The senate confirms or doesn’t confirm the nominee.
A presidential term ends Jan 20.
The Senate changes Jan 3 every two years.
If the president and senate are different parties, there can theoretically be no new Justice confirmed until they are of the same party.
Here is a pretty good chart showing the Supreme Court nominations by president and those nominees confirmed, not confirmed, withdrew or declined to serve.
https://www.senate.gov/legislative/nominations/SupremeCourtNominations1789present.htm