ELI5: Explain Like I'm 5

Day count convention

Have you ever heard adults talking about how many days there are in a month or a year? Well, sometimes they have to count the days in a special way, which they call a day count convention.

Think of it like this: Imagine you have a jar with 30 marbles inside, and you want to know how many marbles you have to take out of the jar each day for a month. But sometimes, you have to count the days in the month differently, depending on what you are trying to do with those marbles.

For example, let's say you want to know how much money you have to pay at the end of one month for borrowing some marbles from your friend. Your friend wants you to pay a little bit of money for each day you have the marbles. But what if there are different numbers of days in each month? To solve this problem, adults created a day count convention, which is a special way of counting days in different months.

One of the most common day count conventions is called 30/360. This means that you count 30 days in each month, and there are always 360 days in a year. It helps people figure out how much money they need to pay or receive for interest on loans or investments.

Another day count convention is called Actual/360. This means you count the actual number of days in each month, and there are still 360 days in a year. This convention is more accurate than 30/360, but it can be a bit more complicated to use.

So, a day count convention is like a special way of counting days so that people can figure out how much money they need to pay or receive for borrowing or lending things. It helps them make things easier and more accurate.