You can use the ChronoUnit.DAYS enum to calculate the days between two LocalDateTime instances in Java. It provides the between() method to calculate the amount of time between two temporal objects:

// Create date instances
LocalDateTime startDateTime = LocalDateTime.parse("2022-02-12T10:40");
LocalDateTime endDateTime = LocalDateTime.parse("2022-11-12T10:40");

// Calculate the difference
long days = ChronoUnit.DAYS.between(startDateTime, endDateTime);

// Print days
System.out.println("Days between " + startDateTime + " and " + endDateTime + ": " + days);
// Days between 2022-02-12T10:40 and 2022-11-12T10:40: 273

The ChronoUnit enum class was introduced in Java 8 to represent individual date and time units such as day, month, year, week, hour, minutes, etc.

The between() method returns a negative number as a difference in days if the start is after the end date, as shown below:

System.out.println(ChronoUnit.DAYS.between(endDateTime, startDateTime)); // -273

You can also use the ChronoUnit enum to calculate the difference between two LocalDateTime objects in weeks, months, and years:

System.out.println(ChronoUnit.WEEKS.between(startDateTime, endDateTime)); // 39
System.out.println(ChronoUnit.MONTHS.between(startDateTime, endDateTime)); // 9
System.out.println(ChronoUnit.YEARS.between(startDateTime, endDateTime)); // 0

Read this article to learn more about calculating the difference between two dates in Java.

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