Fix convert calendar with different dimension name

doc/whats-new.rst

@@ -27,6 +27,8 @@ Bug fixes
 
 - Fix Pydap Datatree backend testing. Testing now compares elements of (unordered) two sets (before, lists) (:pull:`10525`).
   By `Miguel Jimenez-Urias <https://github.com/Mikejmnez>`_.
+- Fix ``KeyError`` when passing a ``dim`` argument different from the default to ``convert_calendar`` (:pull:`10544`).
+  By `Eric Jansen <https://github.com/ej81>`_.
 
 
 Documentation

xarray/coding/calendar_ops.py

@@ -213,7 +213,7 @@ def convert_calendar(
         out[dim] = new_times
 
         # Remove NaN that where put on invalid dates in target calendar
-        out = out.sel(time=out[dim].notnull())
+        out = out.sel({dim: out[dim].notnull()})
 
         if use_cftime:
             # Reassign times to ensure time index of output is a CFTimeIndex

xarray/tests/test_calendar_ops.py

@@ -239,6 +239,18 @@ def test_convert_calendar_errors():
         convert_calendar(da, "standard", dim="x")
 
 
+def test_convert_calendar_dimension_name():
+    src = DataArray(
+        date_range("2004-01-01", "2004-01-31", freq="D", calendar="noleap"),
+        dims=("date",),
+        name="date",
+    )
+
+    out = convert_calendar(src, "proleptic_gregorian", dim="date")
+
+    np.testing.assert_array_equal(src, out)
+
+
 def test_convert_calendar_same_calendar():
     src = DataArray(
         date_range("2000-01-01", periods=12, freq="6h", use_cftime=False),