Java,将Date转换为String并返回错误的Date [英] Java, converting Date to String and back produced wrong Date
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问题描述
我正在尝试将 Date
转换为 String
,然后再次转换为 Date
。但是我发现最终日期与原始日期不同,这有什么用?
I am trying to convert a Date
to String
and then back again to Date
. However I found out that the final date is different from the original date, what gives?
//1975-06-20
Calendar cal = Calendar.getInstance();
cal.set(Calendar.YEAR, 1975);
cal.set(Calendar.MONTH, 5);
cal.set(Calendar.DAY_OF_MONTH, 20);
cal.set(Calendar.HOUR, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
System.out.println(cal);
Date originalDate = cal.getTime();
System.out.println("Date 1: " + originalDate.toString());
SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy");
Date date = sdf.parse(originalDate.toString());
System.out.println("Date 2: " + date.toString());
以上代码的输出为:
cal: java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Singapore",offset=28800000,dstSavings=0,useDaylight=false,transitions=9,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=1975,MONTH=5,WEEK_OF_YEAR=26,WEEK_OF_MONTH=5,DAY_OF_MONTH=20,DAY_OF_YEAR=179,DAY_OF_WEEK=4,DAY_OF_WEEK_IN_MONTH=4,AM_PM=1,HOUR=0,HOUR_OF_DAY=16,MINUTE=0,SECOND=0,MILLISECOND=333,ZONE_OFFSET=28800000,DST_OFFSET=0]
Date 1: Fri Jun 20 12:00:00 SGT 1975
Date 2: Fri Jun 20 11:30:00 SGT 1975
推荐答案
可能是由于1982年新加坡的时区更改(+ 30分钟)。
Probably because of the timezone change in Singapore on 1982 (+ 30 minutes).
http://www.timeanddate.com/worldclock /timezone.html?n=236&syear=1980
在解析日期时,SimpleDateFormat将SGT设为UTC + 8,然后将其转换为UTC + 7.5,即1982年之前的SGT。因此,日期偏离了30分钟
The SimpleDateFormat take the SGT as UTC+8 when parsing the date, and convert it to UTC+7.5, which is the SGT before 1982. Hence the date is off by 30 minutes.
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