[JAVA] Calendar 타임존(TimeZone) 및 로케일(Locale) 설정

앱을 만들다 보면 한국시간 기준으로 알림을 주어야하는 경우가 발생한다.  왜 필요한가? 라는 질문을 한다면 해외여행중이고 한국과 다른 시간대를 사용하는 나라에 있다면 그 나라에 있더라도 한국시간으로 알림을 줘야하는 필요성이 있기 때문이다.

기본적으로 날짜 정보를 설정하는 코드를 보자. 대부분 아무런 설정 없이 Calendar클래스의 기본 getInstance() 메소드를 사용한다. 

Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());

Calendar 클래스를 들여다보자. 기본 메소드를 보면 TimeZone과 Locale 적용값이 기본 값으로 설정된다.

    /**
     * Gets a calendar using the default time zone and locale. The
     * <code>Calendar</code> returned is based on the current time
     * in the default time zone with the default
     * {@link Locale.Category#FORMAT FORMAT} locale.
     *
     * @return a Calendar.
     */
    public static Calendar getInstance()
    {
        return createCalendar(TimeZone.getDefault(), Locale.getDefault(Locale.Category.FORMAT));
    }

    /**
     * Gets a calendar using the specified time zone and default locale.
     * The <code>Calendar</code> returned is based on the current time
     * in the given time zone with the default
     * {@link Locale.Category#FORMAT FORMAT} locale.
     *
     * @param zone the time zone to use
     * @return a Calendar.
     */
    public static Calendar getInstance(TimeZone zone)
    {
        return createCalendar(zone, Locale.getDefault(Locale.Category.FORMAT));
    }

    /**
     * Gets a calendar using the default time zone and specified locale.
     * The <code>Calendar</code> returned is based on the current time
     * in the default time zone with the given locale.
     *
     * @param aLocale the locale for the week data
     * @return a Calendar.
     */
    public static Calendar getInstance(Locale aLocale)
    {
        return createCalendar(TimeZone.getDefault(), aLocale);
    }

    /**
     * Gets a calendar with the specified time zone and locale.
     * The <code>Calendar</code> returned is based on the current time
     * in the given time zone with the given locale.
     *
     * @param zone the time zone to use
     * @param aLocale the locale for the week data
     * @return a Calendar.
     */
    public static Calendar getInstance(TimeZone zone,
                                       Locale aLocale)
    {
        return createCalendar(zone, aLocale);
    }

■타임존(TimeZone)과 로케일(Locale) 모두 설정

Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("Asia/Seoul"),Locale.KOREA);


   

■타임존만 변경하고 싶을경우에는 타임존값을 매개변수로 하여 초기화하면 된다.

Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("Asia/Seoul"));


   

■로케일만 변경하고 싶을경우에는 로케일값을 매개변수로 하여 초기화하면 된다.

Calendar calendar = Calendar.getInstance(Locale.KOREA);

■ Calendar에 한국 시간 설정하는 코드

Calendar calendar = Calendar.getInstance();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
sdf.setTimeZone(TimeZone.getTimeZone("Asia/Seoul"));
Date date = getStringToDate(sdf.format(new Date()));
calendar.setTime(date);


    public static  Date getStringToDate( String dateString) {
        Calendar calendar = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
            Date date = sdf.parse(dateString);
            return date;
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

■타임존으로 사용가능한 ID값 조회

Arrays.toString(TimeZone.getAvailableIDs());

■타임존(TimeZone) 정보

TimeZone tz = TimeZone.getTimeZone(“Europe/Prague”);

TimeZone tz = TimeZone. getTimeZone(‘Asia/Tokyo’);

TimeZone tz = TimeZone.getTimeZone(“America/Chicago”);

import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.TimeZone;

public class Time {

    public static void main(String[] args) throws Exception {
 
        SimpleDateFormat formatClock = new SimpleDateFormat("EEEE MM/dd/yyyy");
        //TimeZone tz;
    	//Date date = new Date();
        //DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss (z Z)");
    	//tz = TimeZone.getTimeZone("Asia/Seoul"); df.setTimeZone(tz);
    	//System.out.format("%s%n%s%n%n", tz.getDisplayName(), df.format(date));

        formatClock.setTimeZone(TimeZone.getTimeZone("Asia/Seoul"));
        System.out.println(formatClock.format(new Date()));
        System.out.println(); 
        
        //사용가능한 타임존ID값 조회
        System.out.println(Arrays.toString(TimeZone.getAvailableIDs()));
    }
}

[샘플코드 실행 결과]

Friday 05/29/2020

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