How to calculate "time ago" in Java?

Question

Take a look at the PrettyTime library.

It's quite simple to use:

import org.ocpsoft.prettytime.PrettyTime;

PrettyTime p = new PrettyTime();
System.out.println(p.format(new Date()));
// prints "moments ago"

You can also pass in a locale for internationalized messages:

PrettyTime p = new PrettyTime(new Locale("fr"));
System.out.println(p.format(new Date()));
// prints "à l'instant"

As noted in the comments, Android has this functionality built into the android.text.format.DateUtils class.

Have you considered the TimeUnit enum? It can be pretty useful for this kind of thing

    try {
        SimpleDateFormat format = new SimpleDateFormat("dd/MM/yyyy");
        Date past = format.parse("01/10/2010");
        Date now = new Date();

        System.out.println(TimeUnit.MILLISECONDS.toMillis(now.getTime() - past.getTime()) + " milliseconds ago");
        System.out.println(TimeUnit.MILLISECONDS.toMinutes(now.getTime() - past.getTime()) + " minutes ago");
        System.out.println(TimeUnit.MILLISECONDS.toHours(now.getTime() - past.getTime()) + " hours ago");
        System.out.println(TimeUnit.MILLISECONDS.toDays(now.getTime() - past.getTime()) + " days ago");
    }
    catch (Exception j){
        j.printStackTrace();
    }

I take RealHowTo and Ben J answers and make my own version:

public class TimeAgo {
public static final List<Long> times = Arrays.asList(
        TimeUnit.DAYS.toMillis(365),
        TimeUnit.DAYS.toMillis(30),
        TimeUnit.DAYS.toMillis(1),
        TimeUnit.HOURS.toMillis(1),
        TimeUnit.MINUTES.toMillis(1),
        TimeUnit.SECONDS.toMillis(1) );
public static final List<String> timesString = Arrays.asList("year","month","day","hour","minute","second");

public static String toDuration(long duration) {

    StringBuffer res = new StringBuffer();
    for(int i=0;i< TimeAgo.times.size(); i++) {
        Long current = TimeAgo.times.get(i);
        long temp = duration/current;
        if(temp>0) {
            res.append(temp).append(" ").append( TimeAgo.timesString.get(i) ).append(temp != 1 ? "s" : "").append(" ago");
            break;
        }
    }
    if("".equals(res.toString()))
        return "0 seconds ago";
    else
        return res.toString();
}
public static void main(String args[]) {
    System.out.println(toDuration(123));
    System.out.println(toDuration(1230));
    System.out.println(toDuration(12300));
    System.out.println(toDuration(123000));
    System.out.println(toDuration(1230000));
    System.out.println(toDuration(12300000));
    System.out.println(toDuration(123000000));
    System.out.println(toDuration(1230000000));
    System.out.println(toDuration(12300000000L));
    System.out.println(toDuration(123000000000L));
}}

which will print the following

0 second ago
1 second ago
12 seconds ago
2 minutes ago
20 minutes ago
3 hours ago
1 day ago
14 days ago
4 months ago
3 years ago

  public class TimeUtils {

      public final static long ONE_SECOND = 1000;
      public final static long SECONDS = 60;

      public final static long ONE_MINUTE = ONE_SECOND * 60;
      public final static long MINUTES = 60;

      public final static long ONE_HOUR = ONE_MINUTE * 60;
      public final static long HOURS = 24;

      public final static long ONE_DAY = ONE_HOUR * 24;

      private TimeUtils() {
      }

      /**
       * converts time (in milliseconds) to human-readable format
       *  "<w> days, <x> hours, <y> minutes and (z) seconds"
       */
      public static String millisToLongDHMS(long duration) {
        StringBuffer res = new StringBuffer();
        long temp = 0;
        if (duration >= ONE_SECOND) {
          temp = duration / ONE_DAY;
          if (temp > 0) {
            duration -= temp * ONE_DAY;
            res.append(temp).append(" day").append(temp > 1 ? "s" : "")
               .append(duration >= ONE_MINUTE ? ", " : "");
          }

          temp = duration / ONE_HOUR;
          if (temp > 0) {
            duration -= temp * ONE_HOUR;
            res.append(temp).append(" hour").append(temp > 1 ? "s" : "")
               .append(duration >= ONE_MINUTE ? ", " : "");
          }

          temp = duration / ONE_MINUTE;
          if (temp > 0) {
            duration -= temp * ONE_MINUTE;
            res.append(temp).append(" minute").append(temp > 1 ? "s" : "");
          }

          if (!res.toString().equals("") && duration >= ONE_SECOND) {
            res.append(" and ");
          }

          temp = duration / ONE_SECOND;
          if (temp > 0) {
            res.append(temp).append(" second").append(temp > 1 ? "s" : "");
          }
          return res.toString();
        } else {
          return "0 second";
        }
      }


      public static void main(String args[]) {
        System.out.println(millisToLongDHMS(123));
        System.out.println(millisToLongDHMS((5 * ONE_SECOND) + 123));
        System.out.println(millisToLongDHMS(ONE_DAY + ONE_HOUR));
        System.out.println(millisToLongDHMS(ONE_DAY + 2 * ONE_SECOND));
        System.out.println(millisToLongDHMS(ONE_DAY + ONE_HOUR + (2 * ONE_MINUTE)));
        System.out.println(millisToLongDHMS((4 * ONE_DAY) + (3 * ONE_HOUR)
            + (2 * ONE_MINUTE) + ONE_SECOND));
        System.out.println(millisToLongDHMS((5 * ONE_DAY) + (4 * ONE_HOUR)
            + ONE_MINUTE + (23 * ONE_SECOND) + 123));
        System.out.println(millisToLongDHMS(42 * ONE_DAY));
        /*
          output :
                0 second
                5 seconds
                1 day, 1 hour
                1 day and 2 seconds
                1 day, 1 hour, 2 minutes
                4 days, 3 hours, 2 minutes and 1 second
                5 days, 4 hours, 1 minute and 23 seconds
                42 days
         */
    }
}

more @Format a duration in milliseconds into a human-readable format

This is based on RealHowTo's answer so if you like it, give him/her some love too.

This cleaned up version allows you to specify the range of time you might be interested in.

It also handles the " and " part a little differently. I often find when joining strings with a delimiter it's ofter easier to skip the complicated logic and just delete the last delimiter when you're done.

import java.util.concurrent.TimeUnit;
import static java.util.concurrent.TimeUnit.MILLISECONDS;

public class TimeUtils {

    /**
     * Converts time to a human readable format within the specified range
     *
     * @param duration the time in milliseconds to be converted
     * @param max      the highest time unit of interest
     * @param min      the lowest time unit of interest
     */
    public static String formatMillis(long duration, TimeUnit max, TimeUnit min) {
        StringBuilder res = new StringBuilder();

        TimeUnit current = max;

        while (duration > 0) {
            long temp = current.convert(duration, MILLISECONDS);

            if (temp > 0) {
                duration -= current.toMillis(temp);
                res.append(temp).append(" ").append(current.name().toLowerCase());
                if (temp < 2) res.deleteCharAt(res.length() - 1);
                res.append(", ");
            }

            if (current == min) break;

            current = TimeUnit.values()[current.ordinal() - 1];
        }

        // clean up our formatting....

        // we never got a hit, the time is lower than we care about
        if (res.lastIndexOf(", ") < 0) return "0 " + min.name().toLowerCase();

        // yank trailing  ", "
        res.deleteCharAt(res.length() - 2);

        //  convert last ", " to " and"
        int i = res.lastIndexOf(", ");
        if (i > 0) {
            res.deleteCharAt(i);
            res.insert(i, " and");
        }

        return res.toString();
    }
}

Little code to give it a whirl:

import static java.util.concurrent.TimeUnit.*;

public class Main {

    public static void main(String args[]) {
        long[] durations = new long[]{
            123,
            SECONDS.toMillis(5) + 123,
            DAYS.toMillis(1) + HOURS.toMillis(1),
            DAYS.toMillis(1) + SECONDS.toMillis(2),
            DAYS.toMillis(1) + HOURS.toMillis(1) + MINUTES.toMillis(2),
            DAYS.toMillis(4) + HOURS.toMillis(3) + MINUTES.toMillis(2) + SECONDS.toMillis(1),
            DAYS.toMillis(5) + HOURS.toMillis(4) + MINUTES.toMillis(1) + SECONDS.toMillis(23) + 123,
            DAYS.toMillis(42)
        };

        for (long duration : durations) {
            System.out.println(TimeUtils.formatMillis(duration, DAYS, SECONDS));
        }

        System.out.println("\nAgain in only hours and minutes\n");

        for (long duration : durations) {
            System.out.println(TimeUtils.formatMillis(duration, HOURS, MINUTES));
        }
    }

}

Which will output the following:

0 seconds
5 seconds 
1 day and 1 hour 
1 day and 2 seconds 
1 day, 1 hour and 2 minutes 
4 days, 3 hours, 2 minutes and 1 second 
5 days, 4 hours, 1 minute and 23 seconds 
42 days 

Again in only hours and minutes

0 minutes
0 minutes
25 hours 
24 hours 
25 hours and 2 minutes 
99 hours and 2 minutes 
124 hours and 1 minute 
1008 hours 

And in case anyone ever needs it, here's a class that will convert any string like the above back into milliseconds. It's pretty useful for allowing people to specify timeouts of various things in readable text.

there's a simple way to do this:

let's say you want the time 20 minutes ago:

Long minutesAgo = new Long(20);
Date date = new Date();
Date dateIn_X_MinAgo = new Date (date.getTime() - minutesAgo*60*1000);

that's it..