fn main() {
let ts = std::env::var("SOURCE_DATE_EPOCH")
.ok()
.and_then(|s| s.parse::<u64>().ok())
.map(|epoch| {
let secs = epoch;
let days = secs / 86400;
let rem = secs % 86400;
let h = rem / 3600;
let m = (rem % 3600) / 60;
let s = rem % 60;
let z = days + 719468;
let era = z / 146097;
let doe = z % 146097;
let yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
let y = yoe + era * 400;
let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
let mp = (5 * doy + 2) / 153;
let d = doy - (153 * mp + 2) / 5 + 1;
let mo = if mp < 10 { mp + 3 } else { mp - 9 };
let y = if mo <= 2 { y + 1 } else { y };
format!("{y:04}-{mo:02}-{d:02}T{h:02}:{m:02}:{s:02}Z")
})
.unwrap_or_else(|| format!("build-version={}", env!("CARGO_PKG_VERSION")));
println!("cargo::rustc-env=BUILD_TIMESTAMP={ts}");
}