Time lexer.

DateComparison.java

import java.util.ArrayList;

// Changes a long into a human-readable format.
public class DateComparison {

    int weeks, days, hours, minutes, seconds;
    long time;

    public DateComparison (long earlier, long later) {
        this (later > earlier ? (later - earlier) : (earlier - later));
    }

    public DateComparison (long time) {

        this.time    = Math.abs(time);
        this.weeks   = 0;
        this.days    = 0;
        this.hours   = 0;
        this.minutes = 0;
        this.seconds = 0;

        while (time >= TimeLexer.WEEK) {
            time -= TimeLexer.WEEK;
            ++weeks;
        }

        while (time >= TimeLexer.DAY) {
            time -= TimeLexer.DAY;
            ++days;
        }

        while (time >= TimeLexer.HOUR) {
            time -= TimeLexer.HOUR;
            ++hours;
        }

        while (time >= TimeLexer.MINUTE) {
            time -= TimeLexer.MINUTE;
            ++minutes;
        }

        while (time >= TimeLexer.SECOND) {
            time -= TimeLexer.SECOND;
            ++seconds;
        }

    }

    public int getWeeks () { return weeks; }
    public int getDays () { return days; }
    public int getHours () { return hours; }
    public int getMinutes () { return minutes; }
    public int getSeconds () { return seconds; }

    private String toString () {
        ArrayList<String> result = new ArrayList<String>();
        if (weeks > 0)
            result.add(weeks + (weeks == 1 ? " week" : " weeks"));
        if (days > 0)
            result.add(days + (days == 1 ? " day" : " days"));
        if (hours > 0)
            result.add(hours + (hours == 1 ? " hour" : " hours"));
        if (minutes > 0)
            result.add(minutes + (minutes == 1 ? " minute" : " minutes"));
        if (seconds > 0 && time < TimeLexer.HOUR)
            result.add(seconds + (seconds == 1 ? " second" : " seconds"));

        return result.isEmpty() ? "a moment" : elegantList(result);
    }

    public String elegantList (ArrayList<?> list) {
        String result = list.get(0).toString();
        switch (list.size()) {
            case 1:
                return result;

            case 2:
                return result + " and " + list.get(1).toString();

            default:
                for (int i = 1; i < list.size() - 1; ++i) {
                    result += ", " + list.get(i).toString();
                }

                return result + ", and " + list.get(list.size() - 1).toString();
        }
    }

}

TimeLexer.java

// Parses a time input.
public class TimeLexer {

    long time = 0L;
    static final long SECOND = 1000L, MINUTE = 60000L, HOUR = 3600000L, DAY = 86400000L,
            WEEK = 604800000L;
    static final String TIME_EXPRESSION = "(([0-9]+)( )?(s(e)?(c)?(o)?(n)?(d)?|m(i)?(n)?(u)?(t)?(e)?" +
            "|h(o)?(u)?(r)?|d(a)?(y)?|w(e)?(e)?(k)?|y(e)?(a)?(r)?)(s)?( )?)+";

    public TimeLexer (String input) throws Exception {

        if (!input.matches(TIME_EXPRESSION))
            throw new Exception("Illegal input!");

        int seconds = 0, minutes = 0, hours = 0, days = 0, weeks = 0;
        String next = "";
        for (int i = 0; i < input.length(); ++i) {
            switch (input.charAt(i)) {
                case 's': seconds += Integer.parseInt(next);
                          break;

                case 'm': minutes += Integer.parseInt(next);
                          break;

                case 'h': hours += Integer.parseInt(next);
                          break;

                case 'd': days += Integer.parseInt(next);
                          break;

                case 'w': weeks += Integer.parseInt(next);
                          break;

                case ' ': break; // Ignore spaces, they cause issues with Integer.parseInt()

                default: next += input.charAt(i);
            }

            if (Character.toString(input.charAt(i)).matches("(i?)[dhmsw]")) {
                int j;
                for (j = i + 1; j < input.length() &&
                    !Character.toString(input.charAt(j)).matches("[0-9]"); ++j);
                next = "";
                i = j - 1;
            }
        }

        time = (seconds * TimeLexer.SECOND) + (minutes * TimeLexer.MINUTE) + (hours * TimeLexer.HOUR)
             + (days * TimeLexer.DAY) + (weeks * TimeLexer.WEEK);

    }

    public long getTime () {
        return time;
    }

    public String toString () {
        return new DateComparison(this.getTime()).toString();
    }

}