But if you live by the Spirit (God) instead of the letter (man) of the law you'd understand, IMO, that the 4th commandment, as all others, are for the benefit of man.
God doesn't need these laws. He set them down to make life easier for man.
In that respect, the 4th commandment can be honored on any day of the week, because the Spirit of the law is to take a full and complete day of REST and of contemplation. It is a gift to set aside toils and responsibility and renew the inner being.
Jesus reminded us, that doesn't mean to ignore all. So we use our God-given common sense and keep EMS, FD, PD, etc. available 24/7, and "should" assure these essential persons, and everyone else, have one day, any day, where they "answer to no man." This should also apply to rabbi's and clergy. They need that day for "true-self" also.
That, IMO, is "keeping the Sabbath" -- keeping the soul at peace...renewing the spirit.