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YYYYMMdd 和 yyyyMMdd 的区别

来自 https://www.v2ex.com/t/633650

YYYY 是表示：当天所在的周属于的年份，一周从周日开始，周六结束，只要本周跨年，那么这周就算入下一年。

If a week is split at the end of the year then it is assigned to the year in which more that half of the days of that week occur.

u year

y year-of-era

Y week-based-year

YYYYMMdd 和 yyyyMMdd 的区别

public static void main(String[] args) {  
    DateFormat df = new SimpleDateFormat("yyyyMMdd");  
    System.out.println(df.format(new Date()));  
    DateFormat df1 = new SimpleDateFormat("YYYYMMdd");  
    System.out.println(df1.format(new Date()));  
    Calendar calendar = Calendar.getInstance();  
    // 2019-12-31  
    calendar.set(2019, Calendar.DECEMBER, 31);  
    Date strDate1 = calendar.getTime();  
    // 2020-01-01  
    calendar.set(2020, Calendar.JANUARY, 1);  
    Date strDate2 = calendar.getTime();  
    // 大写 YYYY  DateFormat formatUpperCase = new SimpleDateFormat("YYYY/MM/dd");  
    System.out.println("2019-12-31 to YYYY/MM/dd: " /+ formatUpperCase.format(strDate1));  
    System.out.println("2020-01-01 to YYYY/MM/dd: " /+ formatUpperCase.format(strDate2));  
    // 小写 YYYY  DateFormat formatLowerCase = new SimpleDateFormat("yyyy/MM/dd");  
    System.out.println("2019-12-31 to yyyy/MM/dd: " /+ formatLowerCase.format(strDate1));  
    System.out.println("2020-01-01 to yyyy/MM/dd: " /+ formatLowerCase.format(strDate2));  
}

原文 https://segmentfault.com/a/1190000021449818

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