God's law says to 'remember' the Sabbath and keep it holy. Papal law says worship on Sunday. The Catholic church is the Harlot and all religions that worship on Sunday are her daughters, spoken of in Revelations.

The Sabbath is kept on Sunday instead of Saturday on account of Easter.  

The reason to observe it, atleast by going to church and churchschool where possible, is that it is when people don't do these seemingly fairly little things that they tend to fall away from their faith.   Of course many of us have to work on Sunday, and not all churches offer services or Communion at other times of the week.

If my church had a satisfactory church school I'd not be here.

When did Jesus keep the Sabbath?

Very interesting question