Here you can find the source of baseFor(TimeZone tz)
private static Date baseFor(TimeZone tz)
//package com.java2s; //License from project: Open Source License import java.util.TimeZone; import java.util.Date; import java.util.Calendar; public class Main { private static Date baseFor(TimeZone tz) { Calendar c = Calendar.getInstance(tz); c.clear();/*www . jav a 2 s . c om*/ c.set(1899, 11, 30, 0, 0, 0); return c.getTime(); } }