New timezone option: seconds since unix epoch #4458

Job	Run time
Python / Build Wheels	15m 33s
Checks / Test Python Docs	36s
Checks / Python lints (ruff, mypy, …)	9m 3s
Checks / C++ formatting check	3m 29s
Checks / C++ tests	6m 26s
Checks / Rerun lints	2m 30s
Checks / Check if running codegen would produce any changes	3m 22s
Checks / Cargo Deny	2m 26s
Checks / Check Rust web build (wasm32 + wasm-bindgen)	2m 36s
Checks / Rust lints (fmt, check, cranky, tests, doc)	3m 54s
Checks / Spell Check	8s
Checks / Lint TOML files	20s
	50m 23s

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