Those people who believe in a young earth (ranges from 6000 to 50000 years old), usually with the Universe being created a small time before the Earth. When confronted with undeniable evidence, the young earth creationist will claim that the universe was created with an appearance of age.

Young earth creationism has arisen from the differences between English and Hebrew. In many English translations, the creation process is grouped by "days". However, the Hebrew text uses the word "yom", merely meaning a period of work. It can mean a minute, a day, a year, or a billion years. Likewise, the words used for morning and evening can mean work start and work end, respectively. (Ancient Hebrew contained few nouns compared to English, so many words have such overlaps). A literal interpretation will see that the time taken for creation is variable, and can easily encompass the scientific date of a universe many billions of years old, and an Earth that is 4-5 billion years old. This particular literal interpretation is the one used by old earth creationists. (I will have to move some of this information to that node when the time comes). A good argument for the variable days is that in Genesis 2:4, the author refers to "the day that the LORD God made the earth and the heavens", which must refer to all the 6 days of creation in Genesis 1. A good one for short days is that usually "yom" means day, so it feels like a more natural interpretation (both interpretations can feel "forced" at times).

Anyway, there are many facets to the young/old earth debate which would take up far too much space, leaving you either overwhelmed or underwhelmed. Check out www.reasons.org for old (this is my source of information), and www.answersingenesis.org for young.

A historical note: young earth creationism was popularized in the 19th century. Previous to that time, even going back as far as the original church fathers, there was no particular opinion on how to interpret the days, because of too many unknowns. Now that we have enough science to test the interpretations, we can get on to debating better things.