Update some date refs

Author: JohnTitor

src/contributing.md

@@ -443,12 +443,12 @@ Just a few things to keep in mind:
     Try to format the date as `<MONTH> <YEAR>` to ease search.
 
   - Additionally, include a machine-readable comment of the form `<!-- date:
-    2021-10 -->` (if the current month is October 2021). We have an automated
+    2022-04 -->` (if the current month is April 2022). We have an automated
     tool that uses these (in `ci/date-check`).
 
-    So, for the month of January 2021, the comment would look like: `As of <!--
-    date: 2021-10 --> October 2021`. Make sure to put the comment *between* `as of`
-    and `October 2021`; see [PR #1066][rdg#1066] for the rationale.
+    So, for the month of April 2022, the comment would look like: `As of <!--
+    date: 2022-04 --> April 2022`. Make sure to put the comment *between* `as of`
+    and `April 2022`; see [PR #1066][rdg#1066] for the rationale.
 
   - A link to a relevant WG, tracking issue, `rustc` rustdoc page, or similar, that may provide
     further explanation for the change process or a way to verify that the information is not

src/conventions.md

@@ -21,7 +21,7 @@ Formatting is checked by the `tidy` script. It runs automatically when you do
 
 If you want to use format-on-save in your editor, the pinned version of
 `rustfmt` is built under `build/<target>/stage0/bin/rustfmt`. You'll have to
-pass the <!-- date: 2021-09 --> `--edition=2021` argument yourself when calling
+pass the <!-- date: 2022-04 --> `--edition=2021` argument yourself when calling
 `rustfmt` directly.
 
 [fmt]: https://github.com/rust-dev-tools/fmt-rfcs

src/salsa.md

@@ -9,7 +9,7 @@ want to watch [Salsa In More
 Depth](https://www.youtube.com/watch?v=i_IhACacPRY), also by Niko
 Matsakis.
 
-> As of <!-- date: 2021-07 --> July 2021, although Salsa is inspired by
+> As of <!-- date: 2022-04 --> April 2022, although Salsa is inspired by
 > (among other things) rustc's query system, it is not used directly in rustc.
 > It _is_ used in chalk and extensively in `rust-analyzer`, but there are no
 > medium or long-term concrete plans to integrate it into the compiler.

src/thir.md

@@ -4,7 +4,7 @@
 
 The THIR ("Typed High-Level Intermediate Representation"), previously called HAIR for
 "High-Level Abstract IR", is another IR used by rustc that is generated after
-[type checking]. It is (as of <!-- date: 2021-08 --> August 2021) only used for
+[type checking]. It is (as of <!-- date: 2022-04 --> April 2022) only used for
 [MIR construction] and [exhaustiveness checking]. There is also
 [an experimental unsafety checker][thir-unsafeck] that operates on the THIR as a replacement for
 the current MIR unsafety checker, and can be used instead of the MIR unsafety checker by passing