creationists believe the earth is 6000 years old, because when the bible says the word day, the think it is a real day(I DONT EXACTLY KNOW HOW IT IS WRITTEN IN ENGLISH,I ONLY KNOW ABOUT THE DUTCH BIBLE)

This is not true.
There is also written that a day can be 1000 years.
Another important thing is that this is a issue of translation the bible.
In the original language, the word day can mean a Time period, even a long time.

Sorry for my bad english!