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How can I add two dates in Java?
Example: The sum of "2010-01-14 19:16:17" "0000-10-03 01:10:05"
would result in "2010-11-17 20:26:22".
I know how to do it using Calendar and adding field by field.
Is any other way to sum them all (year/month/day/hour/minute/second) at once?
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Example: Java program to add two dates Then, we simply clone c1 and add c2 's each DateTime properties one after the other. As you can see, we've added 1 to the months. This is because months start with 0 in Java. Alternatively, you can also use Joda for time/date operations in Java.
In Java, two dates can be compared using the compareTo() method of Comparable interface. This method returns '0' if both the dates are equal, it returns a value "greater than 0" if date1 is after date2 and it returns a value "less than 0" if date1 is before date2.
We can get the dates between two dates with single method call using the dedicated datesUntil method of a LocalDate class. The datesUntill returns the sequentially ordered Stream of dates starting from the date object whose method is called to the date given as method argument.
Calendar. DATE field can be used to add or subtract dates in Java. Positive value passed into add() method will add days into date while negative values will subtract days from date in Java. Similarly Calendar.
If you are using the Date object, you can just do:
Date d1 = ...
Date d2 = ...
long sum = d1.getTime() + d2.getTime();
Date sumDate = new Date(sum);
The code uses the .getTime() method that returns the number of milliseconds since the epoch.
Needless to say the Date class has a lot of problems and should be avoided when possible.
Do you want to sum other types instead?
Update: for Calendar, I would do the following (based on javadocs):
Calendar c1 = ...
Calendar c2 = ...
long sum = c1.getTimeInMillis() + c2.getTimeInMillis();
Calendar sumCalendar = (Calendar)c1.clone();
sumCalendar.setTimeInMillis(sum);
UPDATED: As Steve stated, this works if the Date you presented here assumes that the second date is with respect to the Java epoch. If you do want to start with year "0", then you need to account for that (by subtracting your epoch time).
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Don't sum the time in millis of the two dates!
Date d1 = new Date();
Date d2 = new Date();
Date dTotal = new Date(d1.getTime() + d2.getTime());
System.out.println(dTotal); // Incorrect! Misses about 1970 years.
Just clone the Calendar and add the datetime parts one by one.
Calendar c1 = Calendar.getInstance();
Calendar c2 = Calendar.getInstance();
Calendar cTotal = (Calendar) c1.clone();
cTotal.add(Calendar.YEAR, c2.get(Calendar.YEAR));
cTotal.add(Calendar.MONTH, c2.get(Calendar.MONTH) + 1); // Months are zero-based!
cTotal.add(Calendar.DATE, c2.get(Calendar.DATE));
cTotal.add(Calendar.HOUR_OF_DAY, c2.get(Calendar.HOUR_OF_DAY));
cTotal.add(Calendar.MINUTE, c2.get(Calendar.MINUTE));
cTotal.add(Calendar.SECOND, c2.get(Calendar.SECOND));
cTotal.add(Calendar.MILLISECOND, c2.get(Calendar.MILLISECOND));
System.out.println(cTotal.getTime()); // Correct!
Needless to say, JodaTime is smarter and cleaner with this.
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