I was watching one of the Harry Potter movies on TV and I realized that in most of the Harry Potter books, and even more so in the movies,  the action takes place over a period of a few weeks or maybe a few months.  Yet each one represents a year in Harry's life.  If someone 500 years from now found and read one of those books, would he realize it represented one year?  My guess is probably not.
    Most biblical scholars believe that Jesus' adult ministry lasted two years.  This is based primarily on the belief that the various events listed in the new testament that occurred during his ministry could not represent a period any longer than that.  At least, not if you string them together like a string of pearls and assume there is no significant breaks.  That's an odd assumption considering that there are such huge gaps in His life before His ministry began.
    These same scholars say that Biblical references to crowds of thousands attending one of Jesus' public events are highly exaggerated because a ministering wandering the desert and giving speeches in mostly small towns could not have built up such a following in a year or two.  They may be correct.  But if the ministry of Jesus actually lasted five years, ten years, maybe more, than yes, he could have such large crowds of followers.  And with such large crowds, he would represent a serious threat to the Jewish priests of the temple and the Roman governor who, at the time, selected the priests from those who swore loyalty to Rome and the emperor.
    It is not at all unreasonable to believe that many events during Jesus' ministry went unrecorded.  There were no reporters following him around.  And the apostles wrote little, if anything, at the time.  Most of what was recorded, was passed on orally for a hundred years or more before being written.