Comparing Dates and Times

The classes LocalDate, LocalTime, LocalDateTime have methods for comparing their instances according to their position on the timeline. The methods compare instances as they go in chronological order (or the order of time).

The method compareTo

The method compareTo compares this instance and another one passed as the method’s argument. It returns 0 if they are equal, a negative value if this instance is less than the other, and a positive value if this instance is greater.

Here is an example of comparing two instances of the class LocalDate:

LocalDate date1 = LocalDate.parse("2017-01-02");
LocalDate date2 = LocalDate.parse("2017-12-12");

date1.compareTo(date1); // 0, date1 and date1 are equal
date1.compareTo(date2); // -11, negative value => date1 is less than date2
date2.compareTo(date1); // 11, positive value => date2 is greater than date1

The class LocalTime has the same method, that returns either 0, 1 or -1:

LocalTime time1 = LocalTime.parse("15:30:10");
LocalTime time2 = LocalTime.parse("17:50:30");

time1.compareTo(time1); // 0, time1 and time1 are equal
time1.compareTo(time2); // -1, time1 is less than time2
time2.compareTo(time1); // 1, time2 is greater than time1

as well as LocalDateTime:

LocalDateTime dateTime1 = LocalDateTime.parse("2017-01-01T20:30"); // 1 January 2017, 20:30
LocalDateTime dateTime2 = LocalDateTime.parse("2017-01-02T23:00"); // 2 January 2017, 23:00

dateTime1.compareTo(dateTime1); // 0, dateTime1 and dateTime are equal
dateTime1.compareTo(dateTime2); // -1, dateTime1 is less than dateTime2
dateTime2.compareTo(dateTime1); // 1, dateTime2 is greater than dateTime1

The methods isAfter, isBefore and isEqual

The classes have also some concise methods to compare dates and time on a timeline that return boolean value.

The method isAfter returns true, only if this instance is strictly after another instance passed as the argument, otherwise, the method returns false.
The method isBefore returns true, only if this instance is strictly before an instance passed as the argument, otherwise, the method returns false.
The method isEqual returns true, if instances are equal, otherwise, the method returns false.

Here is an example of comparing two instances of the LocalDate class.

LocalDate date1 = LocalDate.of(2017, 11, 30);
LocalDate date2 = LocalDate.of(2017, 12, 1);

date1.isEqual(date1); // true
date1.isEqual(date2); // false

date1.isBefore(date2); // true
date1.isBefore(date1); // false
date2.isBefore(date1); // false

date2.isAfter(date1); // true
date2.isAfter(date2); // false
date1.isAfter(date2); // false

Here is an example of comparing two instances of the LocalTime class.

LocalTime time1 = LocalTime.of(14, 20); // 14:20
LocalTime time2 = LocalTime.of(15, 55); // 15:55
LocalTime time3 = LocalTime.of(16, 40); // 16:40
        
time1.isBefore(time2); // true
time3.isBefore(time2); // false
time3.isBefore(time3); // false

time2.isAfter(time1);  // true
time2.isAfter(time3);  // false

And here is an example of comparing two instances of the LocalDateTime class.

LocalDateTime dateTime1 = LocalDateTime.parse("2017-12-01T21:30"); // 1 December 2017, 21:30
LocalDateTime dateTime2 = LocalDateTime.parse("2017-12-02T21:30"); // 2 December 2017, 21:30

dateTime1.isEqual(dateTime2); // false
dateTime2.isEqual(dateTime2); // true

dateTime1.isBefore(dateTime2); // true
dateTime1.isAfter(dateTime2); // false
dateTime2.isAfter(dateTime1); // true

Keep in mind, that the class LocalTime doesn’t have the method isEqual. You can use the method equals instead.

We have learned now how to compare standard classes representing dates and time. Unsurprisingly, it can be done in almost the same unified way.