ENH: Support μs Greek small letter mu
State: closed

The abbreviation for microseconds is best represented as μs, using the 0x3bc Greek small letter mu, instead of the 0xb5 Latin Extended micro sign. This aligns with:

* [The International System of Units (SI) brochure](https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf)
* NFKC normalized [Python code](https://peps.python.org/pep-3131/) and [domain names](https://unicode.org/reports/tr36/)
* Section 2.5 Duplicated Characters of [Unicode Technical Report 25](https://www.unicode.org/reports/tr25/)
* The microfarads abbreviation in [Pandas tests](/pandas-dev/pandas/tree/2.2.x/pandas/tests/computation/test_eval.py#L1914)
* Ruff confusable mapping [updates](https://github.com/astral-sh/ruff/pull/4430/files) (currently in the "preview" stage)

Ensure that both Latin Extended and Greek characters are accepted as aliases for microseconds. Prefer the Greek character in a comment. Looking at the UTF8 test data in test_clipboard.py, the degree and registered trademark symbols should sufficiently cover the Latin Extended character block, so prefer the Greek character there too.

- [x] Closes #58472
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests)
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit)
- [ ] [Type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) not applicable
- [x] Added an entry in the latest `doc/source/whatsnew/v3.0.0.rst` file

Recommended changes for when the [RUF001](https://docs.astral.sh/ruff/rules/ambiguous-unicode-character-string/) updates graduate from preview to stable (can't be applied yet because of [RUF100](https://docs.astral.sh/ruff/rules/unused-noqa/)):
```diff
diff --git a/pandas/_libs/tslibs/timedeltas.pyi b/pandas/_libs/tslibs/timedeltas.pyi
index 9fcea5e32d..5cbf061859 100644
--- a/pandas/_libs/tslibs/timedeltas.pyi
+++ b/pandas/_libs/tslibs/timedeltas.pyi
@@ -55,7 +55,7 @@ UnitChoices: TypeAlias = Literal[
     "us",
     "microseconds",
     "microsecond",
-    "µs",  # 0x0b5 Latin Extended micro sign
+    "µs",  # noqa: RUF001 # 0x0b5 Latin Extended micro sign
     "μs",  # 0x3bc Greek small letter mu
     "micro",
     "micros",
diff --git a/pandas/tests/scalar/timedelta/test_constructors.py b/pandas/tests/scalar/timedelta/test_constructors.py
index 138546eb07..adeff7b77a 100644
--- a/pandas/tests/scalar/timedelta/test_constructors.py
+++ b/pandas/tests/scalar/timedelta/test_constructors.py
@@ -294,7 +294,7 @@ def test_construction():
     assert Timedelta("1 millisecond") == timedelta(milliseconds=1)
     assert Timedelta("1 us") == timedelta(microseconds=1)
     # 0x0b5 Latin Extended micro sign
-    assert Timedelta("1 µs") == timedelta(microseconds=1)
+    assert Timedelta("1 µs") == timedelta(microseconds=1) # noqa: RUF001
     # 0x3bc Greek small letter mu
     assert Timedelta("1 μs") == timedelta(microseconds=1)
     assert Timedelta("1 micros") == timedelta(microseconds=1)
```

Labels:

Comments:
Thanks for the PR, but we require a bit more discussion on the enhancement issue from the core team before moving forward with  PR so closing for now, but we can reopen if there's support for this enhancement request