Here you can find the source of getFirstOfMonth(Timestamp t1)
public static Timestamp getFirstOfMonth(Timestamp t1)
//package com.java2s; import java.sql.Timestamp; import java.util.Calendar; import java.util.GregorianCalendar; public class Main { public static Timestamp getFirstOfMonth(Timestamp t1) { Calendar a = new GregorianCalendar(); a.setTime(t1);/*from ww w . j av a 2 s. c om*/ a.set(Calendar.DATE, 1); return new Timestamp(a.getTimeInMillis()); } }