Document arithmetic operations on Instant #45448

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1. bluss

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   A-docsArea: Documentation for any part of the project, including the compiler, standard library, and toolsArea: Documentation for any part of the project, including the compiler, standard library, and tools

   T-libs-api[DEPRECATED; DO NOT USE][DEPRECATED; DO NOT USE]

   on Oct 22, 2017
2. retep998 commented on Oct 24, 2017

   

   retep998

   on Oct 24, 2017

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   The zero point of Instant is not specified and could be any time before the start of the process. If you want to ensure that you do not get any underflow errors, then do not attempt to create an Instant representing a time before the process was spawned.
3. TimNN

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   C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.

   on Oct 24, 2017
4. steveklabnik

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   on Oct 31, 2017
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   A-docsArea: Documentation for any part of the project, including the compiler, standard library, and toolsArea: Documentation for any part of the project, including the compiler, standard library, and tools

   on Jan 10, 2019
6. steveklabnik commented on Jan 10, 2019

   

   steveklabnik

   on Jan 10, 2019

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   @rust-lang/libs: if you can articulate which aspects of this API are guaranteed, I'm happy to document them.
7. sfackler commented on Jan 10, 2019

   

   sfackler

   on Jan 10, 2019

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   1. What meaning does Instant -= Duration have?

   It causes Instant to have the value of an Instant created Duration time before its original value.

   2. What are the preconditions on the instant and the duration, so that it does not panic or cause arithmetic overflow assertions?

   Instant currently wraps the platform-specific monotonic time type, so the overflow bounds depend on the system. Some probably safe assumptions would be to not create Instants from before your process started or Instants more than a century or so in the future. I don't know what we specifically want to guarantee here though.
8. workingjubilee

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   A-timeArea: `std::time`Area: `std::time`

   on Apr 25, 2021
9. bjorn3

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   A-docsArea: Documentation for any part of the project, including the compiler, standard library, and toolsArea: Documentation for any part of the project, including the compiler, standard library, and tools

   on May 15, 2022
10. cvengler

    added 3 commits that reference this issue on Nov 11, 2025

    time: Implement SystemTime::{MIN, MAX}

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    time: Implement SystemTime::{MIN, MAX}

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    time: Implement SystemTime::{MIN, MAX}

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11. JonathanBrouwer

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15. ChrisDenton

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    Rollup merge of #148825 - cvengler:time_systemtime_limits, r=ChrisDenton

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18. clarfonthey

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