build

Fix mtime header parsing #1515

Job	Run time
'twine-check' on py3.x	20s
'mypy' on py3.x	27s
'py-mindeps' on py3.9	26s
test-sdist	2m 11s
Self-Check	10s
ensure-catalog-matches-hook-config	19s
Test on ubuntu, py3.10	1m 47s
Test on ubuntu, py3.12	1m 49s
Test on ubuntu, py3.11	1m 40s
Test on ubuntu, py3.13	2m 13s
Test on ubuntu, py3.9	1m 39s
Test on windows, py3.9	2m 42s
Test on windows, py3.11	3m 1s
Test on windows, py3.13	3m 7s
Test on windows, py3.12	2m 46s
Test on macos, py3.9	1m 17s
Test on macos, py3.10	1m 23s
Test on macos, py3.13	1m 18s
Test on macos, py3.12	1m 5s
Test on windows, py3.10	2m 55s
Test on macos, py3.11	1m 5s
Collate results to check for skipped tests	8s
	33m 48s

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