Dear Adam,
Alex is very busy accepting congratulations for being more verbose, I mean prolific, than the rest of us.

Please allow me to attempt an answer.
Christ rested in the tomb on Saturday. It is still a kind of Sabbath, for this reason. Remember that Sabbath was not only Saturday, but any holy day of rest and worship.
Canonically, for Christians, Sunday is the holy day of rest each week. We are prohibited from keeping Saturday as our weekly regular day of rest.
Saturday is the day on which to remember the dead. Hence, all of the five soul Saturdays throughout the year when we pray for the dead and visit the cemeteries. Home visits to the families of the departed also usually occurred on Saturdays. The Trisagion or Panikhida was done in Churches on Saturday prior to Vespers. (Vespers, liturgically, marks the beginning of Sunday).
In Christ,
Andrew