Hiya!
Brace! I get carried away when these questions are asked, but no worries, pay attention and read what I say and you'll see the answer to your question! When you're comparing geologic times, make sure that you are aware of all of the times, not just the "dinosaurs" time. This can help you compare and differentiate the eras/periods. Earth has been here for a long time, that is a fact. Whether you're religious or not, put your views aside and base only your inferences on the information that is in front of you for the moment please.
Longest to Shortest =
Eon: Phanerozoic <--- Longest (542.0 million years ago)
Era: Cenozoic (65 million years ago)
Period: Paleogene (65-23 million years ago)
Epoch: Oligocene (33.9 million to 23 million years ago)
Age: Chattian + Rupelian <--- Shortest (The Chattian was 28.1 and 23.03 million years ago whereas the Rupelian was 33.9 and 28.1 million years ago)
(These 'ranks/marks' are founded by the genomic revolution tracker. Researches use this little device to track our evolutionary phenomenas/times.
Researchers are now able to sequence all of the DNA of an organism
& it's genome. What they do with this information is compare the
genomes of different organisms and populations. Then you have your list
of times above. As you can see, these are simply facts.)
The dinosaurs were on Earth when? Well some of you may say, "Adam and Eve were also made on Day 6—so dinosaurs lived at the same time as people, not separated by eons of" But sorry to say, not everyone is going to agree with you on that, because dinosaurs lived between 230 and 65 million years ago. That being said, dinosaurs lived during the 'Mesozoic Era' ... I'm also sorry to say that this was many millions of years before the first modern humans 'Homo sapiens' appeared on Earth. Now I'm sure you're all aware of the "theory" called 'Pangaea' where it is believed that there were no continents but only one giant supercontinent. Meaning Northern American, China, Russian, Australia, Southern America, Africa & every other country and continent were connected. Of course this was a while ago though, in fact, during the Jurassic period itself. Which most believe is why the dinosaurs "died off" ... not necessarily did they die off, but they simply evolved to the new grounds they were brought to. As the Pangaea was split up, that meant new vegetation they had to get use to which can easily change an organism's way of life and structure. Back to the Mesozoic Era (Which is your answer clearly), this was divided up into three different periods, Triassic, Jurassic and Cretaceous.
