1. I did not say that truth is determined by the majority. I said that most scientists agree with a 4 billion + years old earth and that the fact that most scientists belief this is a correct, true, fact.
(I don't think humans can discover the truth at all, or well, they can discover it but it will never be possible for us to give the perfect proof for this.)
2. I do now that some people a very long time ago discovered that the year was 365 days long. I also know that some other people discovered that it is 365,25 days. I also know that we now know that the year is 365,256something years old.
Out of these facts, most people would conclude that measuring methodes got more sophisticated over time. Perhaps you conclude that the year got longer during time instead?