From my experience, I would say the original Sabbath is correctly a Saturday, only because I'm dog tired on Saturday and love a big sleep in on a Saturday, Saturdays i usually feel the need for rest, Sundays i usually have more energy.
I don't know about how you guys feel on Saturdays though.
But it really doesn't matter what day people worship on, I'm sure in Jesus's best interest, he would love it if people found time to worship him everyday.
Who knows about the body than the One who created it?
And so, He said to labour for six days, to rest, and hallowed the seventh day. Why? For two reasons, physical and spiritual.
Physical:
God knew that if man constantly worked, his body will eventually deteriorate. Hence, the command to rest on the seventh day. Not only that, He also made the seventh day holy and a day of worship. Therefore, those who believe any day is a worship day is violating the seventh day rest.
Spiritual:
The Seventh Day Sabbath carries with it an ominous warning and consequence, as we saw the example of the man who picked up sticks, and God told Moses to stone the man to death. Just for picking up sticks on the Sabbath? Because, there is a spiritual element between working and resting on the Sabbath.
Today, the Sabbath Day, is Sunday according to Matthew 28:1, and it is a work day. Not of physical but spiritual work, in the sense that we gather together to worship, bring our tithes in as the Lord have prospered us, and hear the Gospel preached. It is also a day to read and study God’s Word, to write letters to loved ones and friends about the Gospel, visit a family member or friend in the hospital and preach the Gospel, and many other things one can do. This whole day is dedicated to God and not just for two or three hours.
Don’t get snared by the schemes of the Devil or unsaved who professes they are Christians and are not. God has chosen a special day for worship and spiritual work and no other. Don’t get me wrong. Any Christian can worship and praise God any day he wishes but Sunday is God’s day (Isaiah 58).
To God Be The Glory