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java 8 - how to calculate difference between two dates or java.time.LocalDate instances
This quick code reference tip with explanation first shows how to calculate the difference between two dates represented by two java.time.LocalDate instances using java.time.Period class. It then shows how to get the interval between the two LocalDate instances in hours, days and years using java.time.temporal.ChronoUnit class. Java 8 code to find difference between LocalDate instances using java.time.Period [su_box title="Code to find difference between LocalDate instances using java.time.Period" style="soft" box_color="#fcba43" title_color="#00000" radius="4" Class="for-shortcodebox"][java]package com.javabrahman.java8.time; import java.time.LocalDate; import java.time.Month; import java.time.Period; public class LocalDateIntervalPeriod { public static void main(String args[]){ LocalDate dateFrom = LocalDate.of(2015, Month.JULY, 12); LocalDate dateTo = LocalDate.of(2016, Month.AUGUST, 22); Period intervalPeriod = Period.between(dateFrom, dateTo); System.out.println("Difference of days: " + intervalPeriod.getDays()); System.out.println("Difference of months: " + intervalPeriod.getMonths()); System.out.println("Difference of years: " + intervalPeriod.getYears()); } }[/java][/su_box]  OUTPUT of the above code[su_note note_color="#1a1a1a" text_color="#DAD9D7"]Difference of days: 10 Difference of months: 1 Difference of years: 1[/su_note] Quick explanation of the above code
  • java.time.Period is a newly introduced class in Java 8. Period holds a 'duration' or 'quantity' of time in Years, months and days.
  • An interval or difference of time between two given dates is a duration of time between the two dates.
  • To get the duration between 2 LocalDate instances we will use the Period.between() method, which has the signature - static Period between(LocalDate startDateInclusive, LocalDate endDateExclusive)
  • The duration of time between two LocalDate instances passed to the method is returned as a Period instance itself by the method.
  • The obtained duration's specific number of days, years and months breakdown can be obtained using getDays(), getMonths() and getYears() instance method of Period.
  • In the above example, the difference or interval between 12-Jul-2015 and 22-Aug-2016 is obtained via the Period.between() method which is assigned to intervalPeriod object of type Period .
  • The obtained intervalPeriod's days, months and years of difference is then printed which is equal to 1 year, 1 month and 10 days.
Java 8 code to find difference between LocalDate instances using java.time.temporal.ChronoUnit [su_box title="Difference between LocalDate instances using java.time.temporal.ChronoUnit" style="soft" box_color="#fcba43" title_color="#00000" radius="4" Class="for-shortcodebox"][java]package com.javabrahman.java8.time; import java.time.LocalDate; import java.time.Month; import java.time.temporal.ChronoUnit; public class LocalDateIntervalChronoUnit { public static void main(String args[]){ LocalDate dateFrom = LocalDate.of(2015, Month.JULY, 12); LocalDate dateTo = LocalDate.of(2016, Month.AUGUST, 22); long intervalYears = ChronoUnit.YEARS.between(dateFrom, dateTo); System.out.println("Total number of years between dates: " + intervalYears); long intervalMonths = ChronoUnit.MONTHS.between(dateFrom, dateTo); System.out.println("Total number of months between dates: " + intervalMonths); long intervalDays = ChronoUnit.DAYS.between(dateFrom, dateTo); System.out.println("Total number of days between dates:" + intervalDays); } }[/java][/su_box]  OUTPUT of the above code[su_note note_color="#1a1a1a" text_color="#DAD9D7"]Total number of years between dates: 1 Total number of months between dates: 13 Total number of days between dates:407[/su_note] Quick explanation of the above code
  • java.time.temporal.ChronoUnit is an Enum. It provides different enum constants for different time units such as ChronoUnit.DAYS, ChronoUnit.MONTHS, ChronoUnit.YEARS and so on.
  • ChronoUnit implements the java.time.temporal.TemporalUnit interface.
  • TemporalUnit has a method between() which has the following signature - long between(Temporal temporal1Inclusive, Temporal temporal2Exclusive)
  • As LocalDate implements Temporal, using the above between() method from TemporalUnit we can find the difference between two LocalDate instances in the desired unit.
  • To invoke the correct between() method implementation of Temporal we will access it via the required ChronoUnit enum constant. For example - For getting the number of days between two dates we will invoke ChronoUnit.DAYS.between() with fromDate and toDate variables passed to it.
  • Similarly, the ChronoUnit.MONTHS.between() and ChronoUnit.YEARS.between() will be used to get the difference between dates in MONTHS and YEARS.
  • So, the difference or interval between 12-Jul-2015 and 22-Aug-2016 equals 407 days OR 13 months OR 1 year.
Important Note regarding choosing between Period and ChronoUnit - The days,months and years obtained through ChronoUnit represent the entire difference individually i.e. total numbers of days between the two dates, total number of months and so on. The Period.between() method, on the other hand, returns the difference together as the number of Years, Months and Days. This implies that, in case of Period, you cannot use any of the days, months or years value individually if you want the exact difference down to the accuracy of the days. [su_note note_color="#fbfbc4" text_color="#000000" radius="4"][/su_note]