Relative Date formatting

public class DateUtils {

    private long secondMillis = 1000,
            minuteMillis = 60 * secondMillis,
            hourMillis = 60 * minuteMillis,
            dayMillis = 24 * hourMillis;

    public String getRelativeTime(Date from, Date to) {
        long fromMillis = from.getTime();
        long toMillis = to.getTime();
        long diffMillis = Math.abs(fromMillis - toMillis);

        if (diffMillis/secondMillis < 60) {
            return diffMillis/secondMillis+"s";
        } else if (diffMillis/minuteMillis < 60) {
            return diffMillis/minuteMillis+"m";
        } else if (diffMillis/hourMillis < 24) {
            return diffMillis/hourMillis+"h";
        } else {
            return diffMillis/dayMillis+"d";
        }
    }

}