【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 
昨天刷v2ex的时候看到标题YYYY-MM-dd什么bug什么的我都没点进去，今天早上到公司，就有测试和我说测出了日期显示bug，我又重新打开了v站看了一眼，哦，恍然大悟
在格式化日期中：
YYYY 是 week-based-year，今天就已经 是2020 年了
yyyy是year-of-era ，今天还是 2019 年
week-based-year的解释：
In a week-based-year, each week belongs to only a single year. Week 1 of a year is the first week that starts on the first day-of-week and has at least the minimum number of days. The first and last weeks of a year may contain days from the previous calendar year or next calendar year respectively.
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。
参考：JAVA中的SimpleDateFormat yyyy和YYYY的区别
来源：oschina
链接：https://my.oschina.net/u/1762811/blog/3151351