Experiments show that with conditions mimicking natural forces, coal forms quickly; in weeks for brown coal to months for black coal. It does not need millions of years. Furthermore, long time periods could be an impediment to coal formation because of the increased likelihood of the permineralization of the wood, which would hinder coalification.

Read more here.

Science is based on observation, and the only reliable means of telling the age of anything is by the testimony of a reliable witness who observed the events. The Bible claims to be the communication of the only One who witnessed the events of Creation: the Creator himself. As such, the Bible is the only reliable means of knowing the age of the earth and the cosmos. In the end we believe that the Bible will stand vindicated and those who deny its testimony will be confounded.

Source: Creation.com