In the Book of Genesis God clearly uses words that convey a 24 hour period.
Genesis 1:8 (NKJV)
[SUP]8 [/SUP] And God called the firmament Heaven. So the evening and the morning were the second day.
If you teach each day was not a 24 hour day and teach each day was a thousand years then you are teaching a heresy. Teaching heresies will keep you from inheriting the Kingdom of God.
Galatians 5:19-21 (NKJV)
[SUP]19 [/SUP] Now the works of the flesh are evident, which are: adultery, fornication, uncleanness, lewdness,
[SUP]20 [/SUP] idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies,
[SUP]21 [/SUP] envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God.
You will not be allowed to inherit the Kingdom of God if you keep on doing the Works of the flesh. This is why I said those who teach a different Gospel will end up in the Lake of Fire.