What do we call the special day of rest and worship in Christianity?

The story behind the answer

Christians traditionally gather on the first day of the week, often called the Lord’s Day, because the New Testament places Jesus’s resurrection on that day. In 321 CE, Emperor Constantine issued an edict mandating a weekly day of rest, reinforcing this practice across the Roman Empire and embedding it in Christian culture.

In the Middle Ages, this day structured community life: church bells summoned people to Mass, trades paused, and markets were limited. It differs from the Jewish Sabbath (from Friday evening to Saturday evening) and from Easter, which is an annual feast celebrating the Resurrection. While some Christian groups observe a Saturday Sabbath, most Christian traditions center weekly worship on the first day.