Comparing dates is a common task when working with time-based data. With Day.js, you can easily check if one date occurs before, after, or at the same moment as another date using the isBefore, isAfter, and isSame methods. These methods allow you to compare dates with different levels of granularity. For example, you might want to check if two dates fall in the same month, regardless of the day, or if one date is before another by year only.

The granularity parameter lets you specify the unit for comparison, such as day, month, or year. This is useful for practical scenarios like checking if two events are in the same calendar month, determining if a deadline has passed, or verifying if a user's birthday is today regardless of the year. By choosing the right granularity, you can tailor your date comparisons to suit your application's needs and provide accurate, meaningful results.