True, but time is not perceived, but observed. One sec will still equal one sec, but what it is called might be different throughout the universe. Even though the speed of time might change depending on the mass, velocity, gravity, etc... of where it's being measured, it is still relative constant.
The problem with all of this, is that I don't see ANYWHERE in the Bible that states that the universe was created in ONE day. I believe if you read Genesis 1:1 THEN go read Genesis 1:2 you will find that there is NO time gap mentioned to let the reader know exactly how much had transpired between the two verses.