时区只是查看日期的不同方式(这是一个固定的时间点).我在这里写了一个小例子(密切关注断言)：
// timezone independent date (usually interpreted by the timezone of
// the default locale of the user machine)
Date now = new Date();
// now lets get explicit with how we wish to interpret the date
Calendar london = Calendar.getInstance(TimeZone.getTimeZone("Europe/London"));
Calendar paris = Calendar.getInstance(TimeZone.getTimeZone("Europe/Paris"));
// now set the same date on two different calendar instance
london.setTime(now);
paris.setTime(now);
// the time is the same
assert london.getTimeInMillis() == paris.getTimeInMillis();
// London is interpreted one hour earlier than Paris (as of post date of 9th May )
String londonTime = london.get(Calendar.HOUR) + ":" + london.get(Calendar.MINUTE);
String londonTZ = london.getTimeZone().getDisplayName(london.getTimeZone().inDaylightTime(london.getTime()), TimeZone.SHORT);
System.out.println(londonTime + " " + londonTZ);
// Paris is interpreted one hour later than Paris (as of post date of 9th May )
String parisTime = paris.get(Calendar.HOUR) + ":" + paris.get(Calendar.MINUTE);
String parisTZ = paris.getTimeZone().getDisplayName(paris.getTimeZone().inDaylightTime(paris.getTime()), TimeZone.SHORT);
System.out.println(parisTime + " " + parisTZ);
此片段的输出是(结果将根据执行日期/时间而有所不同)：
8:18 BST
9:18 CEST
问题中的代码片段根本没有对存储日期做任何事情.通常,数据库是为本机TimeZone配置的.我建议存储一个额外的字段,表示在解释日期时要使用的TimeZone.
修改日期(通常是固定时间点之前/之后的毫秒)通常不是(通常)一个好主意,因为这将是一个有损修改,在一年中的不同时间点会有不同的解释(由于夏令时)时间).
