(目前)有两种 now 方法:Instant::now 和 SystemTime::now.

There are (currently) two now methods: Instant::now and SystemTime::now.

Instant 说:

对单调递增时钟的测量.不透明且仅在 Duration 时有用.

A measurement of a monotonically increasing clock. Opaque and useful only with Duration.

SystemTime 说:

系统时钟的测量值，对于与文件系统或其他进程等外部实体进行通信非常有用.

A measurement of the system clock, useful for talking to external entities like the file system or other processes.

这些都不适合向人类展示.时间困难，格式化时间是额外的复杂性.不属于标准库确实是一件好事，否则它就会有一个无法改进的固定API.

Neither of these is truly appropriate for showing to a human. Time is hard, and formatting time is additional complexity. It's really a good thing that it's not part of the standard library, otherwise it would have a fixed API that couldn't be improved.

如其他地方所述，我建议使用 chrono，继承人 到 time 箱子.

As mentioned elsewhere, I'd recommend using chrono, the heir apparent to the time crate.