In an earlier article, we looked at different ways to get the current date and time in Java. In this article, you'll learn how to add days, months, and years to date using both Java 8 new date and time API as well as legacy Date and Calendar API.

Java 8 Date & Time API

A new date and time API was introduced in Java 8 to fix the flaws in old java.util.Date and java.util.Calendar API. The new API provides utility methods like plusDays() and minusDays() to manipulate LocalDate, LocalDateTime, ZonedDateTime, and OffsetDateTime.

Add Days to LocalDate

The LocalDate class represents a date without time in ISO-8601 format (yyyy-MM-dd). The following example shows how you can add days, years, and months to an instance of LocalDate:

// increment days by 7
LocalDate date = LocalDate.now();
System.out.println("Current Date: " + date);
date = date.plusDays(7);
System.out.println("Date after Increment: " + date);

// increment month, day, year
LocalDate date2 = LocalDate.of(2016, Month.AUGUST, 15);
System.out.println("Original Date: " + date2);
date2 = date2.plusDays(5).plusMonths(3).plusYears(1);
System.out.println("Date after Increment: " + date2);

// minus days, month
LocalDate date3 = LocalDate.parse("2019-12-25");
System.out.println("Original Date: " + date3);
date3 = date3.minusDays(5).minusMonths(5);
System.out.println("Date after Decrement: " + date3);

You should see the following output for the above code snippet:

Current Date: 2019-12-26
Date after Increment: 2020-01-02
Original Date: 2016-08-15
Date after Increment: 2017-11-20
Original Date: 2019-12-25
Date after Decrement: 2019-07-20

Add Days to LocalDateTime

A LocalDateTime represents both date and time without timezone information in ISO-8601 format. To add or subtract days from an instance of LocalDateTime, you can do the following:

// increment days by 15
LocalDateTime datetime = LocalDateTime.now();
System.out.println("Current Date & Time: " + datetime);
datetime = datetime.plusDays(15);
System.out.println("Date & Time after Increment: " + datetime);

// increment month, day, year
LocalDateTime datetime2 = LocalDateTime.of(2015, Month.AUGUST, 5, 12, 45);
System.out.println("Original Date & Time: " + datetime2);
datetime2 = datetime2.plusDays(20).plusMonths(10).plusYears(3);
System.out.println("Date & Time after Increment: " + datetime2);

// minus days, month
LocalDateTime datetime3 = LocalDateTime.parse("2019-12-25T15:18:25");
System.out.println("Original Date & Time: " + datetime3);
datetime3 = datetime3.minusDays(5).minusMonths(5);
System.out.println("Date & Time after Decrement: " + datetime3);

The output of the above code snippet looks like below:

Current Date & Time: 2019-12-26T18:07:15.607
Date & Time after Increment: 2020-01-10T18:07:15.607
Original Date & Time: 2015-08-05T12:45
Date & Time after Increment: 2019-06-25T12:45
Original Date & Time: 2019-12-25T15:18:25
Date & Time after Decrement: 2019-07-20T15:18:25

Add Days to ZonedDateTime

The ZonedDateTime represents a date and time with a timezone in ISO-8601 format (e.g 2016-12-15T10:15:30+01:00[Europe/Paris]). Here is an example that shows how to add and minus days from an instance of ZonedDateTime:

// increment days by 25
ZonedDateTime datetime = ZonedDateTime.now(ZoneId.systemDefault());
System.out.println("Current Date & Time: " + datetime);
datetime = datetime.plusDays(25);
System.out.println("Date & Time after Increment: " + datetime);

// increment month, day, year
ZonedDateTime datetime2 = ZonedDateTime.of(2010, 5, 5, 12, 45, 0, 0, ZoneId.of("Asia/Karachi"));
System.out.println("Original Date & Time: " + datetime2);
datetime2 = datetime2.plusDays(5).plusMonths(2).plusYears(2);
System.out.println("Date & Time after Increment: " + datetime2);

// minus days, month
ZonedDateTime datetime3 = ZonedDateTime.parse("2016-12-15T10:15:30+01:00[Europe/Paris]");
System.out.println("Original Date & Time: " + datetime3);
datetime3 = datetime3.minusDays(15).minusMonths(8);
System.out.println("Date & Time after Decrement: " + datetime3);

The above code snippet will print the following on the console:

Current Date & Time: 2019-12-26T18:12:28.358+05:00[Asia/Karachi]
Date & Time after Increment: 2020-01-20T18:12:28.358+05:00[Asia/Karachi]
Original Date & Time: 2010-05-05T12:45+05:00[Asia/Karachi]
Date & Time after Increment: 2012-07-10T12:45+05:00[Asia/Karachi]
Original Date & Time: 2016-12-15T10:15:30+01:00[Europe/Paris]
Date & Time after Decrement: 2016-03-30T10:15:30+02:00[Europe/Paris]

Add Days to OffsetDateTime

OffsetDateTime is another class from Java 8 new date and time API that represents a date and time with an offset from UTC/Greenwich in the ISO-8601 format (e.g. 2017-12-30T23:15:30-05:00).

The following example demonstrates how you can add or minus days, months, and years from an object of OffsetDateTime:

// increment days by 14
OffsetDateTime datetime = OffsetDateTime.now();
System.out.println("Current Date & Time: " + datetime);
datetime = datetime.plusDays(14);
System.out.println("Date & Time after Increment: " + datetime);

// increment month, day, year
OffsetDateTime datetime2 = OffsetDateTime.of(2014, 12, 15, 23, 45, 55, 0, ZoneOffset.of("+03:30"));
System.out.println("Original Date & Time: " + datetime2);
datetime2 = datetime2.plusDays(15).plusMonths(5).plusYears(4);
System.out.println("Date & Time after Increment: " + datetime2);

// minus days, month
OffsetDateTime datetime3 = OffsetDateTime.parse("2017-12-30T23:15:30-05:00");
System.out.println("Original Date & Time: " + datetime3);
datetime3 = datetime3.minusDays(10).minusMonths(6);
System.out.println("Date & Time after Decrement: " + datetime3);

Here is how the output looks like:

Current Date & Time: 2019-12-26T18:18:43.725+05:00
Date & Time after Increment: 2020-01-09T18:18:43.725+05:00
Original Date & Time: 2014-12-15T23:45:55+03:30
Date & Time after Increment: 2019-05-30T23:45:55+03:30
Original Date & Time: 2017-12-30T23:15:30-05:00
Date & Time after Decrement: 2017-06-20T23:15:30-05:00

Old Date & Calendar API

Before Java 8, java.util.Date and java.util.Calendar classes were used for handling dates and times. To add or minus days from an instance of Date, you can use the Calendar.add() method as shown below:

// date pattern
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");

// increment current date by 7 days
Date date = new Date();
System.out.println("Current Date: " + formatter.format(date));

// use `Calendar` to add days
Calendar c = Calendar.getInstance();
c.setTime(date);
c.add(Calendar.DATE, 7);

// print date after increment
System.out.println("Date after Increment: " + formatter.format(c.getTime()));

The above code will output the following:

Current Date: 2019-12-26
Date after Increment: 2020-01-02

Here is another example that shows how you can parse a string to a date and then add or minus days, months, years, seconds, and hours from an instance of Date:

try {
    // date pattern
    SimpleDateFormat formatter = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss");

    // parse string to date
    Date date = formatter.parse("17-Jul-2018 05:15:45");
    System.out.println("Original Date: " + formatter.format(date));

    // use `Calendar` to add days, months, years
    Calendar c = Calendar.getInstance();
    c.setTime(date);
    c.add(Calendar.DATE, 7);
    c.add(Calendar.MONTH, -2); // minus months
    c.add(Calendar.YEAR, 1);
    c.add(Calendar.HOUR, 2);
    c.add(Calendar.MINUTE, 12);
    c.add(Calendar.SECOND, 45);

    // print date after increment
    System.out.println("Date after Increment: " + formatter.format(c.getTime()));

} catch (ParseException ex) {
    ex.printStackTrace();
}

Now if you execute the above code, you should see the following output:

Original Date: 17-Jul-2018 05:15:45
Date after Increment: 24-May-2019 07:28:30

Conclusion

In this article, we looked at different ways to add and subtract different date and time units like days, months, and years from a date. Java 8 new date and time API provides plenty of utility methods for manipulating dates and times. We learned to use plusDays() and minusDays() methods to add or minus days from an instance of LocalDate, LocalDateTime, ZonedDateTime, and OffsetDateTime.

Finally, we also looked at how to use Calendar.add() method to add or subtract a specified amount of time from an instance of the legacy Date class.

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