It is rather fitting. Death entered into the world from those created on the sixth day and on the sixth day, God Himself experienced death. On the sixth day, human beings were given a way to escape the death that they inflicted upon themselves.
I always used to think that Saturday was the sixth day, but that is incorrect. The first day of the week is Sunday. Just look at a calendar. The first day of every week is Sunday.
Many times, God uses symbolism. Jesus was resurrected on the morning of Sunday, the first day. This symbolizes a new creation. He is a new creation and if we align our self with Jesus, we can be brought into this new creation. Creation started on the first day, so a new creation occurred on the first day as well.
“So whoever is in Christ is a new creation: the old things have passed away; behold, new things have come.” – [2 Corinthians 5:17]