How to subtract X days from a date using Java calendar?

Question

Anyone know a simple way using Java calendar to subtract X days from a date?

I have not been able to find any function which allows me to directly subtract X days fr

Answer 1

Eli Courtwright second solution is wrong, it should be:

Calendar c = Calendar.getInstance();
c.setTime(date);
c.add(Calendar.DATE, -days);
date.setTime(c.getTime().getTime());

Answer 2

I believe a clean and nice way to perform subtraction or addition of any time unit (months, days, hours, minutes, seconds, ...) can be achieved using the java.time.Instant class.

Example for subtracting 5 days from the current time and getting the result as Date:

new Date(Instant.now().minus(5, ChronoUnit.DAYS).toEpochMilli());

Another example for subtracting 1 hour and adding 15 minutes:

Date.from(Instant.now().minus(Duration.ofHours(1)).plus(Duration.ofMinutes(15)));

If you need more accuracy, Instance measures up to nanoseconds. Methods manipulating nanosecond part:

minusNano()
plusNano()
getNano()

Also, keep in mind, that Date is not as accurate as Instant.

Answer 3

Instead of writing my own addDays as suggested by Eli, I would prefer to use DateUtils from Apache. It is handy especially when you have to use it multiple places in your project.

The API says:

addDays(Date date, int amount)

Adds a number of days to a date returning a new object.

Note that it returns a new Date object and does not make changes to the previous one itself.

Answer 4

You could use the add method and pass it a negative number. However, you could also write a simpler method that doesn't use the Calendar class such as the following

public static void addDays(Date d, int days)
{
    d.setTime( d.getTime() + (long)days*1000*60*60*24 );
}

This gets the timestamp value of the date (milliseconds since the epoch) and adds the proper number of milliseconds. You could pass a negative integer for the days parameter to do subtraction. This would be simpler than the "proper" calendar solution:

public static void addDays(Date d, int days)
{
    Calendar c = Calendar.getInstance();
    c.setTime(d);
    c.add(Calendar.DATE, days);
    d.setTime( c.getTime().getTime() );
}

Note that both of these solutions change the Date object passed as a parameter rather than returning a completely new Date. Either function could be easily changed to do it the other way if desired.

Answer 5

Anson's answer will work fine for the simple case, but if you're going to do any more complex date calculations I'd recommend checking out Joda Time. It will make your life much easier.

FYI in Joda Time you could do

DateTime dt = new DateTime();
DateTime fiveDaysEarlier = dt.minusDays(5);

Answer 6

Someone recommended Joda Time so - I have been using this CalendarDate class http://calendardate.sourceforge.net

It's a somewhat competing project to Joda Time, but much more basic at only 2 classes. It's very handy and worked great for what I needed since I didn't want to use a package bigger than my project. Unlike the Java counterparts, its smallest unit is the day so it is really a date (not having it down to milliseconds or something). Once you create the date, all you do to subtract is something like myDay.addDays(-5) to go back 5 days. You can use it to find the day of the week and things like that. Another example:

CalendarDate someDay = new CalendarDate(2011, 10, 27);
CalendarDate someLaterDay = today.addDays(77);

And:

//print 4 previous days of the week and today
String dayLabel = "";
CalendarDate today = new CalendarDate(TimeZone.getDefault());
CalendarDateFormat cdf = new CalendarDateFormat("EEE");//day of the week like "Mon"
CalendarDate currDay = today.addDays(-4);
while(!currDay.isAfter(today)) {
    dayLabel = cdf.format(currDay);
    if (currDay.equals(today))
        dayLabel = "Today";//print "Today" instead of the weekday name
    System.out.println(dayLabel);
    currDay = currDay.addDays(1);//go to next day
}