ANSWER: We know that dinosaurs existed because there is a significant amount of evidence that they did in the fossil record. One frequent question that people have is where chronologically do they fit in. If man has existed for only a short time period (usually about 6,000 to 10,000 years ago) then how do we explain the long ages that science has assigned to these animals? Did the earliest known dinosaurs begin to appear in the Triassic period some 245 million years ago? When exactly did they live?
The typical answer to the question of when dinosaurs were made are, most times, based on misconceptions concerning the chronology as outlined in the scriptures. A common misconception is that EVERYTHING that was created was created when man was formed from the dust of the ground. The Bible reveals that there was a creation PRIOR to Adam and Eve. Even though Man was made on the sixth day of creation he was NOT the first living organism to be created! This is often overlooked because of an improper understanding of the first two verse in Genesis.
Although MAN is only a few thousand years old, the EARTH is much older. How much older? We are not sure because the Bible simply does not give us that type of information.
According to scripture, the first chapter of Genesis is not a creation but a RE-creation of things. The Hebrew word (Strong's Concordance #H1961) from which we get the English word "was" in the second verse of Genesis, the first chapter, is more accurately rendered as the phrase 'had become.' A more accurate Biblical translation, then, of Genesis' first two verses (with a few notes) would be the following.
In the beginning (referring to God's initial creation of all things) God created the heavens and the earth. The earth HAD BECOME (sometime after God's initial creation) without form and void (due to Lucifer's rebellion and war against God) . . .
An example of the same Hebrew word (Strong's #H1961) used above but rendered in the NKJV, NIV, NASB, HCSB and other translations as "became" or "had become" can be found in the seventh verse of Genesis chapter 2.
The first two verses of Genesis 1 reveals that the earth was created with various forms of life, including the dinosaurs, and then became a cosmic wasteland. After this occurred we find the earth was covered in a deep mantle of water. ALL life that had been originally created became extinct, including giant reptiles. The earth was as the scripture says "without form and void." Then God recreated and refashioned the earth to be able to support human life.
Although the Bible does not state the time span between the first two verses of Genesis 1, the earth does not necessarily have to be extremely old. Very long spans of time are generally used by those who wish to support the evolutionary theory or a version thereof. Since what most people define as evolution did not occur, because our Creator God made everything in existence, large chunks of time are simply not necessary.
Man's best dating methods, so far, are really only guesses since they are based on assumptions that do not take into account how earth's chaotic past has skewed their 'evidence.' An example of an event in the past that skewed the evidence used for dating is Noah's flood delineated in the book of Genesis, 6th chapter.
God made the dinosaurs well before He made Adam and Eve to live. Sometime after this event the whole world became a convulsing and chaotic MESS due to Satan's rebellion and war against God to try and take his throne (Revelation 12:7). These giant animals that children find so fascinating had been killed off before what amounts to a re-creation of all things (Genesis 1, 2). Because of Lucifer's rebellious ways God had to remake the entire world since that it would support his pinnacle of creation - MAN!