001 package org.hackystat.utilities.time.period; 002 003 004 /** 005 * Tag interface for <code>Day</code>, <code>Week</code>, <code>Month</code> objects. 006 * 007 * @author (Cedric) Qin Zhang 008 */ 009 public interface TimePeriod extends Comparable<Object> { 010 011 /** 012 * Returns the first day in this TimePeriod. 013 * @return The first day associated with this time period. 014 */ 015 public Day getFirstDay(); 016 }