Okay kiddo, so you know how adults work to make money to buy things they need like food, clothes, and a home, right? Well, a long, long time ago, people didn't have clocks or watches to tell time, so they used something called "hour glasses" - a glass with sand inside that took a certain amount of time to flow from one end to the other.
Now, in medieval times, a man named Fitzpayn created a schedule to help workers know when to start and stop working. This schedule was called the "Fitzpayn hours." However, over time, people started to use a different schedule called the "grey hours," which was used by monks and involved dividing the day into eight periods called "canonical hours."
Eventually, the two schedules were combined to create the "grey-fitzpayn hours" schedule, which was used by craftsmen and workers in medieval times. This schedule divided the day into 24 hours, but the hours were not all the same length because the amount of daylight changed throughout the year. The hours of the day were also named after different activities, like "prime," "tierce," "sext," "non," and "vespers," and workers would start and stop working at certain times based on which hour it was.
So, there you have it - grey-fitzpayn hours is an old schedule that people used to tell time and regulate their work schedules a long time ago, and it involved dividing the day into different periods and naming the hours after different activities!