Date Difference in Human Readable format in Java Date Difference in Human Readable format in Java

Ashish Lahoti
Java
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In this quick tutorial, we’ll learn how to print the difference between two dates in human-readable format in Java.

Requirement

We want to create a utility method in Java that returns the difference between two Dates in human-readable format i.e. in Years, Months, and Days.

These are few examples of expected difference between two dates:-

Start Date End Date Expected Difference
2000-01-01 2001-01-01 1 Year
2000-01-01 2020-01-01 20 Years
2000-01-01 2000-02-01 1 Month
2000-01-01 2000-11-01 10 Months
2000-01-01 2000-01-02 1 Day
2000-01-01 2000-01-26 25 Days
2000-01-01 2001-02-02 1 Year, 1 Month and 1 Day
2000-01-01 2005-05-04 5 Years, 4 Months and 3 Days
2000-01-01 2001-01-26 1 Year and 25 Days
2000-01-01 2000-05-04 4 Months and 3 Days

Let’s build a utility method to achieve this.

Date Utility Method

Let’s create a Java utility method DateUtils.getDiffInHumanReadableFormat(startDate, endDate) to find the difference between two LocalDate in human-readable format i.e. in Years, Months, and Days.

package com.example.util;

import java.time.LocalDate;
import java.time.Period;

public class DateUtils {

  public static String getDiffInHumanReadableFormat(LocalDate startDate, LocalDate endDate) {
    Period period = Period.between(startDate, endDate);
    StringBuilder token = new StringBuilder();
    appendUnits(token, period.getYears(), "Year");
    yearSeparator(period, token);
    appendUnits(token, period.getMonths(), "Month");
    monthSeparator(period, token);
    appendUnits(token, period.getDays(), "Day");
    return token.toString().trim();
  }

  // Helper Methods

  private static void appendUnits(StringBuilder token, int units, String unitName) {
    if (units > 0) {
      token.append(units).append(" ").append(unitName);
      if (units > 1) token.append("s");
    }
  }

  private static void yearSeparator(Period period, StringBuilder token) {
    if (period.getYears() > 0 && period.getMonths() > 0) {
      token.append(period.getDays() > 0 ? ", " : " and ");
    }
  }

  private static void monthSeparator(Period period, StringBuilder token) {
    boolean appendAnd = (period.getMonths() > 0 && period.getDays() > 0) ||
            (period.getMonths() == 0 && period.getYears() > 0 && period.getDays() > 0);
    if (appendAnd) token.append(" and ");
  }
}

Let’s write a test case to validate our method:-

package com.example.util;

import org.junit.jupiter.api.Test;
import java.time.LocalDate;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class DateUtilsTest {

  @Test
  void testGetHumanReadableDiff() {
    assertEquals("1 Year",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2001, 1, 1)));
    assertEquals("20 Years",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2020, 1, 1)));
    assertEquals("1 Month",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2000, 2, 1)));
    assertEquals("10 Months",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2000, 11, 1)));
    assertEquals("1 Day",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2000, 1, 2)));
    assertEquals("25 Days",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2000, 1, 26)));
    assertEquals("1 Year, 1 Month and 1 Day",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2001, 2, 2)));
    assertEquals("5 Years, 4 Months and 3 Days",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2005, 5, 4)));
    assertEquals("5 Years and 4 Months",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2005, 5, 1)));
    assertEquals("1 Year and 25 Days",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2001, 1, 26)));
    assertEquals("4 Months and 3 Days",
            DateUtils.getDiffInHumanReadableFormat(LocalDate.of(2000, 1, 1), LocalDate.of(2000, 5, 4)));
  }
}

That’s it! You can copy the code and use it. Thanks for reading!