# Nightly version for a specific rust compiler version
**URL:** https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434
**Category:** compiler
**Created:** [February 22, 2025, 1:16am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434 "2025-02-22T01:16:07Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@ARK](https://internals.rust-lang.org/u/ARK)
#### Post date: [February 22, 2025, 1:16am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434/1 "2025-02-22T01:16:07Z")
How to find the nightly build date for a specific rust compiler version? For example for rustc 1.84.1 which nightly to install? Thanks
---
### Author:  [@steffahn](https://internals.rust-lang.org/u/steffahn)
#### Post date: [February 22, 2025, 1:34am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434/2 "2025-02-22T01:34:03Z")
Rustc `1.84.1` isn’t identical to _any_ nightly version, because of how it was created.
(all dates & times are about UTC)
- it branched from the master branch on 22 November, 2024
- I’m not sure off the top of my head how to get this date in the most “official” way, but at least the third-party website releases.rs does [have this information](https://releases.rs/docs/1.84.0/) easily available
- _edit:_ out of curiosity, as an examples I looked up how `cargo bisect-rustc` does this kind of “translation” – apparently the approach there is to have a `rust` repository available, look up the _tag_ for the release, and then determine the merge-base, i.e. the last common ancestor, with `master`, the date of which should give this information
- if you don’t need it _precisely_, then you can take the release date of the previous stable version; and the branch from master should be slightly less than 1 week before that [with the current release process, 6 days]; e.g looking at [Tags · rust-lang/rust · GitHub](https://github.com/rust-lang/rust/tags), I find `1.83.0` released on `Nov 28, 2024`, which is 6 days later than the “22 November” I mentioned above.
- it then existed on the beta branch for 6 weeks
- during this time, all important regression issues, e.g. code that no longer compiles properly, or compilation times being slow, some newly-introduced language or library feature having flaws discovered last-minute, etc… would be determined
- and fixed by backporting the patches from master to beta
- after this, it was released as `1.84.0`, designated to be the stable version for the next 6 weeks, starting with its release date 9 January, 2025
- during this time, if regression issues are found that have been overlooked during beta, when those are considered important enough, they can be fixed on stable ~ in this case, a handful of such issues were actually found & fixes applied, which is why `1.84.1` was released on 30 January, 2025
All of these backports/fixes made `1.84.1` more and more different from the nightly version that it started at! Nonetheless, the nightly version(s) from when the corresponding beta branched from master is still generally the closest possible approximation.
The branching from master doesn’t happen at the same time as when nightly build happen. If `1.84` branched from master some time _during_ November 22nd, then this means that’s some point _between_ `nightly-2024-11-22` (which is built around midnight using the last commit of November 21st, which is thus the date you see from its `rustc --version` printout) and `nightly-2024-11-23` (which is built around midnight from the last commit of November 22st).
* * *
For a basic introduction to the release train, see this appendix chapter in the book:
[G - How Rust is Made and “Nightly Rust” - The Rust Programming Language](https://doc.rust-lang.org/book/appendix-07-nightly-rust.html)
---
### Author:  [@Vorpal](https://internals.rust-lang.org/u/Vorpal)
#### Post date: [February 22, 2025, 7:45am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434/3 "2025-02-22T07:45:47Z")
> [@steffahn](#):
>
> [...] which is built around midnight using the last commit of [...]
Out of interest: which midnight? UTC?
---
### Author:  [@steffahn](https://internals.rust-lang.org/u/steffahn)
#### Post date: [February 22, 2025, 8:48am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434/4 "2025-02-22T08:48:03Z")
yes, there's a small UTC remark near the top of my reply already 😉
---
### Author:  [@Vorpal](https://internals.rust-lang.org/u/Vorpal)
#### Post date: [February 22, 2025, 10:19am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434/5 "2025-02-22T10:19:45Z")
Very small. Too small to notice.
---
### Author:  [@ARK](https://internals.rust-lang.org/u/ARK)
#### Post date: [February 22, 2025, 10:35am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434/6 "2025-02-22T10:35:59Z")
This post is very insightful. Thanks 👍
---
### Author:  [@jmjoy](https://internals.rust-lang.org/u/jmjoy)
#### Post date: [February 26, 2025, 6:02am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434/7 "2025-02-26T06:02:51Z")
Perhaps you can check [https://releases.rs/](https://releases.rs/) to find the release date of a version that's two versions prior to the stable version, in order to locate the corresponding nightly version.
---
### Author:  [@system](https://internals.rust-lang.org/u/system)
#### Post date: [August 20, 2026, 6:03am UTC](https://internals.rust-lang.org/t/nightly-version-for-a-specific-rust-compiler-version/22434/8 "2026-08-20T06:03:26Z")
This topic was automatically closed 540 days after the last reply. New replies are no longer allowed.