A long time ago, people used to measure time using things like the position of the sun or the size of a candle, but they didn't have clocks like we do now.
One day, some really smart people created a big book called the "Chronography of 354." This book had a bunch of pictures and lists that showed the days and months of the year, important religious events, and even some drawings of the stars!
It was like a super fancy calendar that had all the important dates and times written down, so people knew when to celebrate holidays or go to important events.
This book was really important because it helped people keep track of time and organize their lives. In fact, we still use some of the same ideas from the Chronography of 354 today!