Okay kiddo, so Martin Anstey was a really smart guy who studied history a long time ago. He was interested in figuring out when different events in history happened, like when important people were born or when big battles were fought. He was especially interested in figuring out when Jesus was born and when he died.
Now, back then, people didn't use calendars like we do today. They didn't have a January, February, March, etc. Instead, they used something called a "Julian calendar" which was named after a guy named Julius Caesar who made it up. But there was a problem with the Julian calendar – it didn't always match up perfectly with how long a year actually is. This meant that over time, the dates on the calendar got all messed up.
Martin Anstey wanted to figure out how to fix this problem. He spent a lot of time doing research and looking at old documents. And finally, he came up with a new way of figuring out exactly when different events in history happened. He called it the "Anstey Method."
Basically, what Martin Anstey did was he looked at all the different historical events and tried to find patterns. For example, he looked at when people were writing letters to each other or when they were celebrating certain holidays. By figuring out how often these things happened, he could get a better idea of how long a year was back then.
Using this information, Martin Anstey was able to create a new calendar that was much more accurate than the old Julian calendar. His calendar was called the "Anno Mundi" or "AM" calendar, which means "in the year of the world." In this calendar, the year that Jesus was born was year 1, and every year after that was numbered higher.
Even though we don't use the Anstey Method or the AM calendar anymore, Martin Anstey's work was really important. It helped people understand more about history and how time works. And that's pretty cool!