.NET/Windows中埃及等时区DST转换差1秒问题咨询

我们的.NET应用在处理夏令时（DST）间隙导致的无效时间问题时，编写了一套自动将时间调整至间隙后有效时间的代码（未使用Nodatime）。该代码在绝大多数时区下都能正常工作，但在Egypt Standard Time、Pacific SA Standard Time（智利圣地亚哥）和Middle East Standard Time这三个时区出现异常。

涉及时区的调整规则 #

Egypt Standard Time
   Adjustment rule #10
      Start Date: Wednesday, January 1, 2025
      End Date: Wednesday, December 31, 2025
      Time Change: 1:00 hours
      Annual Start: The Last Thursday of April at 11:59 PM (04/24/2025)
      Annual End: The Last Thursday of October at 11:59 PM

Pacific SA Standard Time
   Adjustment rule #17
      Start Date: Sunday, January 1, 2023
      End Date: Friday, December 31, 9999
      Time Change: 1:00 hours
      Annual Start: The First Saturday of September at 11:59 PM (09/06/2025)
      Annual End: The First Saturday of April at 11:59 PM

Middle East Standard Time
   Adjustment rule #17
      Start Date: Wednesday, January 1, 2025
      End Date: Wednesday, December 31, 2025
      Time Change: 1:00 hours
      Annual Start: The Last Saturday of March at 11:59 PM (03/29/2025)
      Annual End: The Last Saturday of October at 11:59 PM

异常表现 #

这三个时区的DST开始转换时间为23:59:59，结束转换时间为次日00:59:59，DaylightDelta（间隙时长）均为1小时。但将DST开始转换时间加1小时后转换为UTC时，.NET会抛出如下无效时间异常：

System.ArgumentException: The supplied DateTime represents an invalid time.  For example, when the clock is adjusted forward, any time in the period that is skipped is invalid.

测试代码 #

TimeZoneInfo.ConvertTimeToUtc(new DateTime(2025, 4, 25, 0, 59, 59),
    TimeZoneInfo.FindSystemTimeZoneById("Egypt Standard Time"));

TimeZoneInfo.ConvertTimeToUtc(new DateTime(2025, 9, 7, 0, 59, 59),
    TimeZoneInfo.FindSystemTimeZoneById("Pacific SA Standard Time"));

TimeZoneInfo.ConvertTimeToUtc(new DateTime(2025, 3, 30, 0, 59, 59),
    TimeZoneInfo.FindSystemTimeZoneById("Middle East Standard Time"));

进一步观察 #

其他时区的下限（TimeZoneInfo.TransitionTime.DaylightTransitionStart）为包含性，上限（TimeZoneInfo.TransitionTime.DaylightTransitionEnd）为排他性，但这三个时区的上限似乎是包含性的——因为将测试时间加1秒后，UTC转换可正常执行，不会抛出异常。

已知.NET使用的时区信息来自完全更新的Windows 10系统，请问这是Windows时区信息的Bug、.NET的Bug，还是这三个时区的DST间隙上限存在特殊的包含性规则？

注：StackOverflow上《TimeZone Offset is incorrect for "Egypt Standard Time" on Windows 10》的问题未解答本问题，因其涉及不同Windows版本的差异，而本问题发生在同一电脑和Windows版本下。

内容的提问来源于stack exchange，提问作者Matthew Rodatus