The greatest mistake is the belief that mistakes are rare. This is untrue. We all make mistakes and do so frequently. Here are a few involving our thinking.
The concept of BC and AD was apparently invented by a monk around the year 533 who thought Jesus was born 533 years before the day he invented the system. BC stood for “before Christ” and AD for the Latin “anno domini.” the year of our Lord. He was mistaken. He forgot that the gospel Matthew 2:16 states that Jesus’ parents Joseph and Mary were visited by an angel and told them that Herod would attempt to kill Jesus. Herod died in the year 4 BCE. So according to Matthew, Jesus was born while Herod was still alive. The date of birth of Jesus is not stated in any gospel or in any historical reference, but most biblical scholars assume a year of birth between 6 and 4 BCE, between four and six years before Christ.
Is it more proper to use BCE rather than BC? Yes, for two reasons. First because the concept of “before Christ” ignores the fact that not everyone believes that Jesus was the messiah and should be venerated. We need to respect everyone. Second because as shown above, the monk’s notion was clearly wrong. BCE is now used by many scholars and thoughtful persons. It simply means “before the common (meaning, commonly used) era.”
The names New Testament and Old Testament are other mistakes. The names were invented to disparage the Jewish Bible. The idea is that the Christian Bible surpasses and supersedes the Jewish Bible which is old and no longer of any value. This is incorrect. Many Christians find much in the Hebrew Bible that is valuable. We should not use these terms. We should use the names “Hebrew Bible” and “Greek Bible” or the Hebrew name “Tanakh” and “Christian Canon,” or something similar.
It is a mistake to think that the Christian messiah’s name is Jesus. There are different ways of transliterating (rendering) words from Hebrew to another language. One of the frequently used introductory Hebrew letters is the letter yud, the tenth letter of the Hebrew alphabet. In Hebrew, the yud is pronounced like a Y in English, as in the Hebrew Yehuda, Yehudi, Yehoshua, Yeshu, Yerushalayim, Yishmael, and Yisrael. German scholars in recent centuries for unknown reasons did not render most of these words with a Y, but with a J. As a result, most of the words in the list above became Judah, Jew, Joshua, Jesus, and Jerusalem. But the Germans were not consistent. They also transliterated the Hebrew yud with an I. Examples are the last two in the above list which are rendered as Ishmael and Israel.
Many people mistakenly think that Jesus created Christianity which would differ from Judaism. The truth is that scholars are unsure exactly what Jesus’ goal was, but all agree that he had no intention to change Judaism. According to Matthew 5:18, part of the Sermon on the Mount, Jesus declares that he came not to destroy the law but to fulfill it. He says in Matthew 5:18, “For truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished.” He reinforces his goal in 5:19, “Whosoever, therefore, shall break [even] one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.”
 The word “iota” is Greek, a language that Jesus did not speak. Iota is the ninth and smallest letter of the Greek alphabet. The writer of Matthew, written in Greek, used this Greek word rather than the Hebrew yud which is the tenth and smallest letter in the Hebrew alphabet, close to being only a point in size