Modular arithmetic is a branch of mathematics used to predict the outcomes of cyclic events such as days of the week, market days, months of the year, time etc.

Modular Arithmetic is a special base arithmetic in which only the remainder is reported. That is, it can be considered as remainder arithmetic. For example, considering the number of days of the week on a circular dial or circular clock face as shown below.

If we take Sunday as the starting point (0), Monday (1) and so on clockwise around the dial, we can find any day we want.