how to use the differenceincalendaryears function from date-fns in javascript

The differenceInCalendarYears function from the date-fns library is used to calculate the difference between two dates in calendar years. Here is an example of how to use it in JavaScript:

index.tsx
const dateFns = require('date-fns');

const startDate = new Date('2010-01-01');
const endDate = new Date('2020-01-01');

const differenceInYears = dateFns.differenceInCalendarYears(endDate, startDate);

console.log(differenceInYears); // Output: 10
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In this example, we first import the date-fns library with require. We then create two date objects, startDate and endDate. We pass these dates as arguments to the differenceInCalendarYears function to calculate the difference between them in calendar years. The result is stored in the differenceInYears variable, which we then log to the console.

Note that the differenceInCalendarYears function only calculates the number of calendar years between two dates, not the number of years, months, or days. If you need a more precise calculation, you can use the differenceInYears function instead, which calculates the difference in years, including fractions of a year.