Okay kiddo, so imagine you have a special day celebrating your birthday. Well, saints (which are people who lived good and holy lives) have their own special days too, called feast days. And these feast days are celebrated on the calendar of saints.
Now, the calendar of saints is like a big list or schedule of all these different feast days. And it's important because it helps people know when to celebrate and honor each saint.
But here's the thing: there are a LOT of saints. So instead of having a separate day for each one, the calendar groups them together. For example, all the saints who were martyrs (which means they died for their faith) might be celebrated on the same day.
And sometimes, certain saints are more important than others. So they might get their own day, or their feast day might be celebrated with more attention and festivities.
Basically, the calendar of saints helps us remember and honor all the holy people who have lived before us. And it reminds us that even though they're not with us anymore, their example and devotion can still inspire us today.