Removing the calculation of periods also from _time_index #623

Job	Run time
mypy	3m 35s
py3.13 \| macos \| unit tests	9m 8s
py3.13 \| macos \| integration tests	14m 2s
py3.13 \| ubuntu \| unit tests	10m 8s
py3.13 \| ubuntu \| integration tests	13m 28s
py3.13 \| windows \| unit tests	18m 11s
py3.13 \| windows \| integration tests	35m 10s
py3.10 \| ubuntu \| unit tests	10m 50s
py3.10 \| ubuntu \| integration tests	13m 32s
py3.11 \| ubuntu \| unit tests	10m 13s
py3.12 \| ubuntu \| unit tests	10m 30s
merge-test-artifacts	3s
	2h 28m 50s

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