//! Times as `oxy` prints them: UTC, `YYYY-MM-DD HH:MM:SSZ`.

pub fn when(ms: u64) -> String {

    let secs = (ms / 1000) as i64;

    let days = secs.div_euclid(86_400);

    let rem = secs.rem_euclid(86_400);

    // Civil-from-days (Howard Hinnant), UTC.

    let z = days + 719_468;

    let era = z.div_euclid(146_097);

    let doe = z - era * 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 m = if mp < 10 { mp + 3 } else { mp - 9 };

    let y = if m <= 2 { y + 1 } else { y };

    format!("{y:04}-{m:02}-{d:02} {:02}:{:02}:{:02}Z", rem / 3600, (rem % 3600) / 60, rem % 60)

}