However, this dictionary sides with jardeko and jarcento. http://esperanto-panorama.net/vortaro/eoen.htm
Yet, elsewhere I have noticed that "jarcento" is translated as a "century" and "centjaro" is translated as a "hundred years" and "jardeko" is translated as a "decade" and "dekjaro" is translated as "ten years". It makes sense to me, because when people speak quickly how will you know if they are saying centjaro or cent jaro and there is a difference between a hundred years and a century, so I am glad that with jarcento that I will understand right away. If I am talking about the 15th century for instance, that would not be right to say the 15th hundred years.
The 1500's would be after the 15th century which spans from 1401-1500. The first century goes from year 1 through 100, so a century has a very specific start and finish while a hundred years might start and end differently. https://en.wikipedia.org/wiki/15th_century
This dictionary acknowledges that sometimes centjaro=jarcento, for example when talking about a man's age. http://reta-vortaro.de/revo/ "He is going to be a century old!" = "He is going to be a hundred years old."
In The Sixteen Rules of Esperanto Grammar, compound words are explained in rule 11 as having the main word last. http://babel.ucsc.edu/~hank/105/Esperanto16.pdf