BUG: plotting with non-nano TimedeltaIndex (#63237)

Author: jbrockmendel

doc/source/whatsnew/v3.0.0.rst

@@ -1249,6 +1249,7 @@ Plotting
 - Bug in :meth:`Series.plot` preventing a line and bar from being aligned on the same plot (:issue:`61161`)
 - Bug in :meth:`Series.plot` preventing a line and scatter plot from being aligned (:issue:`61005`)
 - Bug in :meth:`Series.plot` with ``kind="pie"`` with :class:`ArrowDtype` (:issue:`59192`)
+- Bug in plotting with a :class:`TimedeltaIndex` with non-nanosecond resolution displaying incorrect labels (:issue:`63237`)
 
 Groupby/resample/rolling
 ^^^^^^^^^^^^^^^^^^^^^^^^

pandas/plotting/_matplotlib/converter.py

@@ -1107,7 +1107,7 @@ def __init__(self, unit: TimeUnit = "ns"):
     axis: Axis
 
     @staticmethod
-    def format_timedelta_ticks(x, pos, n_decimals: int, exp: int) -> str:
+    def format_timedelta_ticks(x, pos, n_decimals: int, exp: int = 9) -> str:
         """
         Convert seconds to 'D days HH:MM:SS.F'
         """