TimeUtils.java

import java.util.concurrent.TimeUnit;

public class TimeUtils {

    public static String toRelative(long timeStamp) {

        long delta = System.currentTimeMillis() - timeStamp;

        if (delta < 0) {
            return "just now";
        }

        long seconds = TimeUnit.MILLISECONDS.toSeconds(delta);
        long minutes = TimeUnit.MILLISECONDS.toMinutes(delta);
        long hours = TimeUnit.MILLISECONDS.toHours(delta);
        long days = TimeUnit.MILLISECONDS.toDays(delta);

        if (seconds < 45) {
            return "just now";
        } else if (seconds < 90) {
            return "a minute ago";
        } else if (minutes < 45) {
            return minutes + " minutes ago";
        } else if (minutes < 90) {
            return "an hour ago";
        } else if (hours < 24) {
            return hours + " hours ago";
        } else if (hours < 42) {
            return "a day ago";
        } else if (days < 30) {
            return days + " days ago";
        } else if (days < 45) {
            return "a month ago";
        } else {
            long months = days / 30;

            if (months < 12) {
                return months + " months ago";
            }

            long years = months / 12;
            return years == 1 ? "a year ago" : years + " years ago";
        }
    }

    public static void main(String Args[]) {
        long now = System.currentTimeMillis();

        System.out.println("Testing TimeUtils:");

        System.out.println("................");

        System.out.println("Current Time: " + toRelative(now));
        System.out.println("40 seconds ago: " + toRelative(now - 40_000));
        System.out.println("10 minutes ago: " + toRelative(now - (10 * 60 * 1000L)));
        System.out.println("5 hours ago: " + toRelative(now - (5 * 60 * 60 * 1000L)));
        System.out.println("3 days ago: " + toRelative(now - (3L * 24 * 60 * 60 * 1000)));
        System.out.println("400 days ago: " + toRelative(now - (400L * 24 * 60 * 60 * 1000)));

    }
}