1 AD, which stands for Anno Domini, marks the year traditionally considered to be the birth year of Jesus Christ. In the Roman calendar, this year falls within the Julian calendar era, which was introduced by Julius Caesar in 45 BC. The Julian calendar established a year of 365 days with a leap year every four years, which helped to standardize the way years were counted and recorded.
During this time, the Roman Empire was at its height, and the calendar system in place was crucial for administrative purposes, agriculture, and festivals. 1 AD plays a significant role in historical timelines as it sets the foundation for the Gregorian calendar that we use today. The years before Christ are denoted as BC (Before Christ), leading up to this pivotal year which signifies the start of the AD era.