Whether it's a day, or a thousand years, God will accomplish His purpose. We are also told that the days of creation could not have been 24-hour period because too much activity occurred on sixth day. God can do anything he wants without time restraints. The account in Genesis Two is clear, both the man and the woman were created on the sixth day. The days of creation should be accepted as literal, 24- hour periods because the context demands such a rendering.
Hebrew word is yom.
Moses could have used a word that would have expressed long periods of time, but purposely did not use it. There should be no need to look any further for an answer. So the sons of Israel shall observe the sabbath, to celebrate the sabbath throughout their generations as a perpetual covenant. Again notice verse 17. Moses obviously believed that God created the universe we live in in six days.