Dionysius Exiguus, a 6th century monk, is credited with calculating the birth year of Jesus and introducing the use of the Anno Domini (AD) era. He believed that Jesus was born in the year 753 AUC (Ab Urbe Condita, or "From the Founding of the City," meaning Rome) which he converted to the date of 1 AD. However, Dionysius made an error in his calculation by not taking into account that there was no year "0" between the years 1 BC and 1 AD.
Recent discoveries and historical research suggest that Jesus was likely born several years earlier than 1 AD. One key piece of evidence is the reference in the Gospel of Luke to a census that was conducted "while Quirinius was governor of Syria" (Luke 2:2). This census is believed by many scholars to have been conducted in 6 AD and it would mean that Jesus was born before that date. It's also worth noting that although the Bible doesn't provide a reason for the travel, the traditional understanding of the biblical account is that the journey to Bethlehem, and Jesus's birth there, fulfill the Old Testament prophecy in Micah 5:2 which speaks of a ruler coming from Bethlehem.
Additionally, the death of King Herod the Great, who is said to have ordered the Massacre of the Innocents, is said to have occurred in 4 BC.
Furthermore, many scholars today, based on the historical and scriptural evidence, believe that Jesus was likely born between 6-4 BC. The exact date, however, is difficult to pin down and it's likely that the gospel authors were more focused on the theological and spiritual significance of Jesus' birth rather than providing an exact date.
Herod the Great, the Roman-appointed King of Judaea, is said to have died in 4 BC. The exact date of his death is uncertain, but it is thought to have occurred around the end of March or beginning of April of that year.
The cause of Herod's death is also not well-documented in contemporary historical records. However, the ancient historian Flavius Josephus, in his "Antiquities of the Jews," describes Herod's death as a slow and painful one. According to Josephus, Herod suffered from a severe case of chronic kidney and bladder disease, and other symptoms such as a fever, severe itching, and a severe abdominal pain. Josephus also states that Herod's physicians were unable to cure him, and that his suffering continued for five days.
Herod's death was also a political event, as it triggered a succession crisis, with his sons fighting for the throne. The events following his death would be connected with the reign of his sons and family, with them also fighting for the power, and also lead to the Roman involvement in the region.
It's important to note that some of the details of Herod's death and illness, as reported by Josephus, have been considered by some scholars as being likely embellished or exaggerated, and the exact circumstances of his death remain uncertain.
As for the date of Jesus' death, it is traditionally held to be around AD 30. It is commonly accepted that Jesus died under the governorship of Pontius Pilate, which is historically dated to the years 26-36 AD. The gospels accounts also give hints that Jesus died during the Jewish Passover and in some years that would fall on AD 30. However, without solid historical documentation it is difficult to specify the exact year.
Overall, while the traditional date of Jesus' birth is celebrated on December 25, it is now widely accepted by scholars that Jesus was likely born several years earlier than the commonly accepted date of 1 AD. Despite the historical and scriptural evidence pointing to a date in the range of 6-4 BC and historians providing the date of death around AD 30, the exact date of Jesus' birth and death remains uncertain due to lack of concrete historical documentation and the focus of the gospel authors on the spiritual and theological significance rather than exact historical dating.