On a calendar invented and published by man. What makes you so sure that our calendar is aligned with the original creation?
You are calling God a liar. He instituted the seven day week. There is no known celestial, solar or earthly event that dictates seven days to a week. In the beginning . . 6 days of creation and one day of rest. It started with God. God would not command man to observe a day that he could not figure out which day it is he's supposed to be observing. God commanded Sabbath worship. He gave us a calendar to show us what day it is. The world tells you to worship another day (or no day). It is your choice to obey God or not.