build.rs

fn main() {
    println!("cargo:rustc-env=ANYR_BUILD_TIME_UTC={}", utc_now());
}

/// Build time as `YYYY-MM-DDTHH:MM:SSZ` (UTC), std-only — civil-from-days per
/// Howard Hinnant's algorithm. Stored in UTC; the CLI renders it in the
/// viewer's local timezone at runtime.
fn utc_now() -> String {
    let secs = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map(|d| d.as_secs() as i64)
        .unwrap_or(0);
    let (y, mo, d, h, mi, s) = civil_from_unix(secs);
    format!("{y:04}-{mo:02}-{d:02}T{h:02}:{mi:02}:{s:02}Z")
}

/// Split a unix timestamp into `(year, month, day, hour, minute, second)` in UTC.
pub fn civil_from_unix(secs: i64) -> (i64, u32, u32, u32, u32, u32) {
    let days = secs.div_euclid(86_400);
    let rem = secs.rem_euclid(86_400);
    let (h, mi, s) = (rem / 3600, (rem % 3600) / 60, rem % 60);
    // Shift the civil epoch so March is month 3; the year then starts in March.
    let z = days + 719_468;
    let era = z.div_euclid(146_097);
    let doe = z.rem_euclid(146_097);
    let yoe = (doe - doe / 1460 + doe / 36_524 - doe / 146_096) / 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 };
    (y, mo as u32, d as u32, h as u32, mi as u32, s as u32)
}