ERR: Improve error message for deprecated frequency aliases in to_offset

pandas/tests/tseries/frequencies/test_frequencies.py

@@ -2,6 +2,8 @@
 
 from pandas._libs.tslibs import offsets
 
+import pandas as pd
+
 from pandas.tseries.frequencies import (
     is_subperiod,
     is_superperiod,
@@ -27,3 +29,9 @@
 def test_super_sub_symmetry(p1, p2, expected):
     assert is_superperiod(p1, p2) is expected
     assert is_subperiod(p2, p1) is expected
+
+
+def test_deprecated_freq_alias_error():
+    # GH#62259
+    with pytest.raises(ValueError, match="Invalid frequency 'H'.*Did you mean 'h'?"):
+        pd.date_range("2012-01-01", periods=3, freq="H")

pandas/tseries/frequencies.py

@@ -27,7 +27,7 @@
 from pandas._libs.tslibs.offsets import (
     DateOffset,
     Day,
-    to_offset,
+    to_offset as _to_offset,
 )
 from pandas._libs.tslibs.parsing import get_rule_month
 from pandas.util._decorators import cache_readonly
@@ -53,6 +53,12 @@
         TimedeltaIndex,
     )
     from pandas.core.arrays.datetimelike import DatetimeLikeArrayMixin
+
+_DEPRECATED_FREQ_ALIASES = {
+    "H": "h",
+    "T": "min",
+    "S": "s",
+}
 # --------------------------------------------------------------------
 # Offset related functions
 
@@ -600,6 +606,20 @@ def _is_weekly(rule: str) -> bool:
     return rule == "W" or rule.startswith("W-")
 
 
+def to_offset(freq):
+    try:
+        return _to_offset(freq)
+    except Exception as err:
+        if isinstance(freq, str) and freq in _DEPRECATED_FREQ_ALIASES:
+            suggestion = _DEPRECATED_FREQ_ALIASES[freq]
+            raise ValueError(
+                f"Invalid frequency '{freq}'. Did you mean '{suggestion}'?"
+            ) from None
+        raise ValueError(
+            f"Invalid frequency: {freq}, failed to parse with error message: {err}"
+        ) from None
+
+
 __all__ = [
     "Day",
     "get_period_alias",