Allow nanoseconds unix epoch, and numeric literal after year format #3536

Job	Run time
alternative_targets (ubuntu-latest, wasm32-unknown-emscripten)	21s
check-docs	20s
alternative_targets (ubuntu-latest, aarch64-apple-ios)	17s
cross-targets (x86_64-unknown-illumos)	1m 4s
alternative_targets (ubuntu-latest, aarch64-linux-android)	17s
cross-tests (ubuntu-latest)	1m 53s
no_std (ubuntu-latest, thumbv6m-none-eabi)	19s
features_check (ubuntu-latest)	21s
no_std (ubuntu-latest, x86_64-fortanix-unknown-sgx)	20s
rust_msrv (ubuntu-latest)	58s
rust_versions (ubuntu-latest, stable)	1m 10s
test_wasip1 (ubuntu-latest, wasm32-wasip1)	21s
test_wasm (ubuntu-latest)	31s
rust_versions (ubuntu-latest, beta)	1m 14s
timezones (ubuntu-latest, ACST-9:30)	1m 21s
rust_versions (ubuntu-latest, nightly)	51s
timezones (ubuntu-latest, EST4)	1m 21s
timezones (ubuntu-latest, UTC0)	1m 18s
timezones (ubuntu-latest, Asia/Katmandu)	1m 17s
timezones (macos-latest, ACST-9:30)	44s
timezones (macos-latest, EST4)	51s
timezones (macos-latest, UTC0)	45s
timezones (macos-latest, Asia/Katmandu)	46s
timezones (windows-latest, ACST-9:30)	1m 50s
timezones (windows-latest, EST4)	1m 53s
timezones (windows-latest, UTC0)	1m 44s
timezones (windows-latest, Asia/Katmandu)	1m 45s
	25m 52s

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