How to find the number of days between two dates in java or groovy?

Question

I have a method which uses following logic to calculate difference between days.

long diff = milliseconds2 - milliseconds1;
long diffDays = diff / (24 * 60 *         


        

Answer 1

In groovy all you need is:

date2 - date1

which returns an integer representing the number of days between the two dates.

Or if you need to guard against reversal of order between the two Date instances (the operation returns negative numbers when the first operand is earlier than the second):

Math.abs(date2 - date1)

The above examples use the groovy date.minus(date) operator implementation which returns the number of days between the two dates.

Example groovy shell session:

$ groovysh
Groovy Shell (2.4.8, JVM: 1.8.0_111)
Type ':help' or ':h' for help.

groovy:000> x = new Date(1486382537168)
===> Mon Feb 06 13:02:17 CET 2017

groovy:000> y = new Date(1486000000000)
===> Thu Feb 02 02:46:40 CET 2017

groovy:000> x - y
===> 4

or if you need a method:

int daysBetween(date1, date2) {
    Math.abs(date2 - date1)
}

Answer 2

Find out the number of days in between two given dates:

@Test

public class Demo3 {

    public static void main(String[] args) {
        String dateStr ="2008-1-1 1:21:28";
        String dateStr2 = "2010-1-2 1:21:28";
        SimpleDateFormat format = new SimpleDateFormat("yyy-MM-dd HH:mm:ss");
        SimpleDateFormat format2 = new SimpleDateFormat("yyy-MM-dd HH:mm:ss");
        try {
            Date date2 = format.parse(dateStr2);
            Date date = format.parse(dateStr);

            System.out.println("distance is :"+differentDaysByMillisecond(date,date2));
        }catch(ParseException e ){
            e.printStackTrace();
        }
    }

//get Days method

    private static int differentDaysByMillisecond(Date date, Date date2) {
        return (int)((date2.getTime()-date.getTime())/1000/60/60/24);
    }

}

Answer 3

Date.metaClass.calculateDays = { Date offset = new Date() ->            
    Long result = null
    Date date = delegate
    use(groovy.time.TimeCategory) {
        result = (offset - date).days as Long
    }            
    result            
}

example of use:

def sdf = new java.text.SimpleDateFormat("yyyy.MM.dd")

sdf.lenient = false

Date date = sdf.parse("2015.10.02")

println date.calculateDays() 

println date.calculateDays(sdf.parse("2015.11.02"))

Answer 4

just parse 9th feb 2011 & 19th feb 2011 into dates using SimpleDateFormat and convert it to start & end millis and apply your calculation

Answer 5

  GregorianCalendar cal1 = new GregorianCalendar(2011,2,9); 
  GregorianCalendar cal2 = new GregorianCalendar(2011,2,19); 
  long ms1 = cal1.getTime().getTime(); 
  long ms2 = cal2.getTime().getTime(); 
  long difMs = ms2-ms1; 
  long msPerDay = 1000*60*60*24; 

  double days = difMs / msPerDay;

Answer 6

For the groovy solution you asked for you should consider using this:

use(groovy.time.TimeCategory) {
   def duration = date1 - date2
   println "days: ${duration.days}, Hours: ${duration.hours}"
}

It's very easy to understand and extremely readable. You asked for a example how this can be used in an easy method which calculates the days between two dates. So here is your example.

class Example {

    public static void main(String[] args) {
        def lastWeek = new Date() - 7;
        def today = new Date()

        println daysBetween(lastWeek, today)
    }

    static def daysBetween(def startDate, def endDate) {
        use(groovy.time.TimeCategory) {
            def duration = endDate - startDate
            return duration.days
        }
    }
}

If you run this example it will print you 7. You can also enhance this method by using before() and after() to enable inverted dates.