Java Calendar Adjust adjustCalendarToLocalTime(Calendar cal)

Description

Needed to rectify the interpretation of timestamp values in calendar objects.

License

Open Source License

Parameter

Parameter	Description
cal	a parameter

Declaration

public static void adjustCalendarToLocalTime(Calendar cal) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.util.Calendar;

import java.util.Date;

import java.util.TimeZone;

public class Main {
    /**/*from   w ww  .  j  a v a  2  s.  c o m*/
     * Needed to rectify the interpretation of timestamp values in calendar
     * objects. Background: timestamps in our log files are meant to be in local
     * time, but are interpreted as UTC when setting the calendar with
     * setTimeInMillis. This method adjusts the calendar by the offset between
     * local time and UTC so that it actually reflects the correct time.
     * 
     * IMPORTANT: This method needs to be called WHENEVER a calendar has been
     * instantiated with setTimeInMillis
     * 
     * @param cal
     */
    public static void adjustCalendarToLocalTime(Calendar cal) {
        Date date = cal.getTime();

        TimeZone tz = TimeZone.getTimeZone("CET");
        long msFromEpochGmt = date.getTime(); // gets the ms from 1970 in UTC
        // (as set with
        // setTimeInMillis)

        // gives you the current offset in ms from GMT at the date
        // msFromEpochGmt
        int offsetFromUTC = tz.getOffset(msFromEpochGmt);

        cal.setTimeInMillis(msFromEpochGmt + offsetFromUTC);
    }
}

Related

1. adjustCalendar(Calendar calendar)
2. adjustDate(Calendar calendar, int differenceInDay)
3. adjustedMillis(Calendar cal)
4. adjustToDayEnd(Calendar cal)
5. adjustToFieldStart(Calendar cal, int[] fields)