php – 为什么有多个时区选择都可以解析为EST？

On the IANA website,they state the following about their upkeep of the timezone database:

The Time Zone Database (often called tz or zoneinfo) contains code and
data that represent the history of local time for many representative
locations around the globe. It is updated periodically to reflect
changes made by political bodies to time zone boundaries,UTC offsets,
and daylight-saving rules. Its management procedure is documented in
BCP 175: Procedures for Maintaining the Time Zone Database.

由于并非所有州都使用夏令时(亚利桑那州,夏威夷,波多黎各,例如不使用夏令时),时区的主题变得更加复杂.

因此,从中得出的结论是,特定城市的时区基于其区域边界,夏令时规则和其他政治因素.因此,仅仅因为一些城市恰好在西部,并不意味着它保证是PST,例如.

此外,通过手动将西部地区设置为PST在技术上可维护性低于设置其实际国家/城市时区标识符的可维护性,因此,如果将来它们的偏移量发生变化,您的应用程序将继续设置正确的时间.