Comment.java

package PACKAGE_NAME;

import java.util.Date;

class Comment {

    private final Date timestamp;
    private final String message;

    public Comment(Date timestamp, String message) {
        this.timestamp = timestamp;
        this.message = message;
    }

    public Date getTimestamp() {
        return timestamp;
    }

    public String getMessage() {
    }
}

MockBackend.java

package PACKAGE_NAME;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Locale;
import java.util.TimeZone;

class MockBackend {

    private static final List<Comment> MOCK_DATA = new ArrayList<>();
    private static final List<Comment> MOCK_DATA_ISO = new ArrayList<>();

    static {
        MOCK_DATA.add(new Comment(date("2016-02-19 06:00"), "Lorem ipsum dolor sit amet, ad antiopam intellegebat eum."));
        MOCK_DATA.add(new Comment(date("2016-02-14 11:55"), "Est viderer mentitum ad. Saepe alienum laboramus eu vel,"));
        MOCK_DATA.add(new Comment(date("2016-02-14 09:00"), "cu odio scribentur concludaturque sed, cu nihil virtute principes has."));
        MOCK_DATA.add(new Comment(date("2016-02-13 12:00"), "Oblique vituperatoribus his no, an mei esse eligendi."));
        MOCK_DATA.add(new Comment(date("2016-02-06 12:00"), "Atqui civibus cu eam, an magna maluisset mei."));
        MOCK_DATA.add(new Comment(date("2016-01-14 18:40"), "Eu usu erat iisque, id vel sale everti."));
        MOCK_DATA.add(new Comment(date("2016-01-13 18:40"), "Ut etiam comprehensam signiferumque his, mel"));
        MOCK_DATA.add(new Comment(date("2015-10-14 18:40"), "an inani laudem eruditi, nec cu putant admodum corrumpit."));
        MOCK_DATA.add(new Comment(date("2014-02-14 18:40"), "No maiorum dissentias consectetuer eos, at animal volutpat quaerendum duo."));
        MOCK_DATA.add(new Comment(date("2014-02-14 18:40"), "Aeque commune ne vel."));
        MOCK_DATA.add(new Comment(date("2014-02-14 18:40"), "Ferri quidam nam ad. Eros temporibus ea duo."));

        //Iso Data Template.
        MOCK_DATA_ISO.add(new Comment(dateIso("2016-02-19T06:00:03Z"), "Lorem ipsum dolor sit amet, ad antiopam intellegebat eum."));
        MOCK_DATA_ISO.add(new Comment(dateIso("2016-02-14T11:55:55Z"), "Est viderer mentitum ad. Saepe alienum laboramus eu vel,"));
        MOCK_DATA_ISO.add(new Comment(dateIso("2016-02-14T09:00:01Z"), "cu odio scribentur concludaturque sed, cu nihil virtute principes has."));
        MOCK_DATA_ISO.add(new Comment(dateIso("2016-02-13T12:00:05Z"), "Oblique vituperatoribus his no, an mei esse eligendi."));
        MOCK_DATA_ISO.add(new Comment(dateIso("2016-02-06T12:00:30Z"), "Atqui civibus cu eam, an magna maluisset mei."));
        MOCK_DATA_ISO.add(new Comment(dateIso("2016-01-14T18:40:10Z"), "Eu usu erat iisque, id vel sale everti."));
        MOCK_DATA_ISO.add(new Comment(dateIso("2016-01-13T18:40:20Z"), "Ut etiam comprehensam signiferumque his, mel"));
        MOCK_DATA_ISO.add(new Comment(dateIso("2015-10-14T18:40:15Z"), "an inani laudem eruditi, nec cu putant admodum corrumpit."));
        MOCK_DATA_ISO.add(new Comment(dateIso("2014-02-14T18:40:50Z"), "No maiorum dissentias consectetuer eos, at animal volutpat quaerendum duo."));
        MOCK_DATA_ISO.add(new Comment(dateIso("2014-02-14T18:40:01Z"), "Aeque commune ne vel."));
        MOCK_DATA_ISO.add(new Comment(dateIso("2014-02-14T18:40:03Z"), "Ferri quidam nam ad. Eros temporibus ea duo."));
    }

    private static Date date(String string) {
        try {
            return new SimpleDateFormat("yyyy-MM-dd HH:mm", Locale.UK).parse(string);
        } catch (ParseException e) {
            throw new IllegalArgumentException(e);
        }
    }

    private static Date dateIso(String string){
        try {
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.getDefault());
            simpleDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
            return simpleDateFormat.parse(string);
        } catch (ParseException e) {
            throw new IllegalArgumentException(e);
        }
    }

    public static List<Comment> loadComments() {
        return MOCK_DATA;
    }

    public static List<Comment> loadIsoComments() {
        return MOCK_DATA_ISO;
    }

}

TimeStampFormatter.java

package PACKAGE_NAME;

import java.util.Date;
import java.util.concurrent.TimeUnit;

import org.joda.time.DateTime;
import org.joda.time.Days;
import org.joda.time.Hours;
import org.joda.time.Minutes;
import org.joda.time.Months;
import org.joda.time.Weeks;
import org.joda.time.Years;

class TimeStampFormatter {

    /**
     * For use with java.util.Date
     */
    public String format(Date timestamp) {
        long millisFromNow = getMillisFromNow(timestamp);

        long minutesFromNow = TimeUnit.MILLISECONDS.toMinutes(millisFromNow);
        if (minutesFromNow < 1) {
            return "just now";
        }
        long hoursFromNow = TimeUnit.MILLISECONDS.toHours(millisFromNow);
        if (hoursFromNow < 1) {
            return formatMinutes(minutesFromNow);
        }
        long daysFromNow = TimeUnit.MILLISECONDS.toDays(millisFromNow);
        if (daysFromNow < 1) {
            return formatHours(hoursFromNow);
        }
        long weeksFromNow = TimeUnit.MILLISECONDS.toDays(millisFromNow) / 7;
        if (weeksFromNow < 1) {
            return formatDays(daysFromNow);
        }
        long monthsFromNow = TimeUnit.MILLISECONDS.toDays(millisFromNow) / 30;
        if (monthsFromNow < 1) {
            return formatWeeks(weeksFromNow);
        }
        long yearsFromNow = TimeUnit.MILLISECONDS.toDays(millisFromNow) / 365;
        if (yearsFromNow < 1) {
            return formatMonths(monthsFromNow);
        }
        return formatYears(yearsFromNow);
    }

    private long getMillisFromNow(Date commentedAt) {
        long commentedAtMillis = commentedAt.getTime();
        long nowMillis = System.currentTimeMillis();
        return nowMillis - commentedAtMillis;
    }

    /**
     * For use with org.joda.DateTime
     */
    public String format(DateTime commentedAt) {
        DateTime now = DateTime.now();
        Minutes minutesBetween = Minutes.minutesBetween(commentedAt, now);
        if (minutesBetween.isLessThan(Minutes.ONE)) {
            return "just now";
        }
        Hours hoursBetween = Hours.hoursBetween(commentedAt, now);
        if (hoursBetween.isLessThan(Hours.ONE)) {
            return formatMinutes(minutesBetween.getMinutes());
        }
        Days daysBetween = Days.daysBetween(commentedAt, now);
        if (daysBetween.isLessThan(Days.ONE)) {
            return formatHours(hoursBetween.getHours());
        }
        Weeks weeksBetween = Weeks.weeksBetween(commentedAt, now);
        if (weeksBetween.isLessThan(Weeks.ONE)) {
            return formatDays(daysBetween.getDays());
        }
        Months monthsBetween = Months.monthsBetween(commentedAt, now);
        if (monthsBetween.isLessThan(Months.ONE)) {
            return formatWeeks(weeksBetween.getWeeks());
        }
        Years yearsBetween = Years.yearsBetween(commentedAt, now);
        if (yearsBetween.isLessThan(Years.ONE)) {
            return formatMonths(monthsBetween.getMonths());
        }
        return formatYears(yearsBetween.getYears());
    }

    private String formatMinutes(long minutes) {
        return format(minutes, " minute ago", " minutes ago");
    }

    private String formatHours(long hours) {
        return format(hours, " hour ago", " hours ago");
    }

    private String formatDays(long days) {
        return format(days, " day ago", " days ago");
    }

    private String formatWeeks(long weeks) {
        return format(weeks, " week ago", " weeks ago");
    }

    private String formatMonths(long months) {
        return format(months, " month ago", " months ago");
    }

    private String formatYears(long years) {
        return format(years, " year ago", " years ago");
    }

    private String format(long hand, String singular, String plural) {
        if (hand == 1) {
            return hand + singular;
        } else {
            return hand + plural;
        }
    }

}