为什么时间戳限制为 2038?

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我刚刚在运行日历脚本时发现，PHP 中的时间戳限制为 2038.这到底是什么意思?为什么是 2038 而不是 2050 或 2039?如果时间戳只计算给定日期(1970 年)的秒数，为什么要限制?

I just found out, running a calendar script, that timestamps in PHP has a limit to 2038. What does it really mean? Why is it 2038 instead of 2050 or 2039? Why a limit if timestamps just count seconds from a given date (1970)?

推荐答案

限制是由大多数 C 库用于表示该计数的 4 字节有符号整数强加的.快速数学(假设 365 天年，不完全正确):

The limit is imposed by the 4 byte signed integers that most C libraries use for representing that count. Quick math (assumes 365 day years, not exactly correct):

2147483648 seconds ~ 68.1 years

这也意味着下限约为 1900.一些库已经开始引入 64 位 epoch 计数，但目前还很少.

This also implies a lower limit of ~1900. Some libraries have started to introduce 64 bit epoch counts, but they are few and far between for the moment.