Fixing non-second timedelta64 bug #398

Job	Run time
mypy	3m 58s
py3.13 \| macos \| unit tests	9m 8s
py3.13 \| macos \| integration tests	12m 31s
py3.13 \| ubuntu \| unit tests	14m 22s
py3.13 \| ubuntu \| integration tests	17m 41s
py3.13 \| windows \| unit tests	18m 52s
py3.13 \| windows \| integration tests	20m 19s
py3.10 \| ubuntu \| unit tests	12m 35s
py3.11 \| ubuntu \| unit tests	12m 51s
py3.10 \| ubuntu \| integration tests	16m 46s
py3.12 \| ubuntu \| unit tests	13m 23s
merge-test-artifacts	1s
	2h 32m 27s

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