Most Christians have not read the creation story in the Bible for many years, and some have never read it directly from the Bible. Most just recall what they learned in Sunday school, or read in a storybook, or heard people say.
Most Christians give Genesis 1 only a casual reading and think that God created everything in six days because it 'clearly' refers to day, days, evening, and morning.
But good Bible study requires more than a casual reading and should be based on meanings in the original Hebrew manuscripts and meanings of the full context (not just individual words), as provided in this study.
Common Christian belief about the days of creation comes more from tradition than from the Bible.
Christians are the only major group of people who believe the world came into existence (essentially as we now find it) in six 24-hour calendar days. Virtually all other people everywhere believe that the earth and its lifeforms developed over long ages of time. It's no wonder that this difference has become a mark of incredulity – and rejection – for Christian faith!
Christians who believe in six-day creation usually assume that Christians who believe in longer time periods have been led astray by modern science. They often say that all Christians believed in six-day creation until Charles Darwin, but that's not true.
Writing 1,700 years ago, Saint Augustine said that it's impossible to tell from the original Genesis manuscripts whether 'day' (Hebrew yō·wm) is 24 hours or a very long period of time (City of God, chapter 11).
Recent prominent conservative theologians – Warfield, Machen, Young, Henry, Archer, Sproul, et al. – have also concluded that the Bible does not compel a 24-hour meaning for each 'day' of creation.
Even though the age-of-earth issue is a big barrier to faith for doubters and unbelievers and a challenge to Bible credibility, it's rarely discussed in church or Bible studies. Christians are not trained to deal with it. The issue is upsetting, and even embarrassing, so people in church circles keep quiet about it, and in silence, they become unaware of the problem or think it's gone away.
Pastors don't want to talk about the age-of-earth issue because they get chastised easily by ingrained church leaders and big donors. Why make waves in the church? Furthermore, pastors are afraid of the issue because it raises two more theological problems:
These are some of the deep reasons why Christians avoid the age-of-earth issue and are unable to answer questions and converse intelligently about it.