Function civil_from_days

nodedb/build.rs:62–76

Howard Hinnant's civil_from_days algorithm. Converts a day count since the Unix epoch (1970-01-01) to a `YYYY-MM-DD` string.

(z: u64)

/// Howard Hinnant's civil_from_days algorithm.
/// Converts a day count since the Unix epoch (1970-01-01) to a `YYYY-MM-DD` string.
fn civil_from_days(z: u64) -> String {
    // Shift epoch from 1970-01-01 to 0000-03-01 for the algorithm.
    let z = z as i64 + 719_468;
    let era = if z >= 0 { z } else { z - 146_096 } / 146_097;
    let doe = z - era * 146_097; // day of era [0, 146096]
    let yoe = (doe - doe / 1460 + doe / 36524 - doe / 146_096) / 365; // year of era [0, 399]
    let y = yoe + era * 400;
    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100); // day of year [0, 365]
    let mp = (5 * doy + 2) / 153; // month prime [0, 11]
    let d = doy - (153 * mp + 2) / 5 + 1; // day [1, 31]
    let m = if mp < 10 { mp + 3 } else { mp - 9 }; // month [1, 12]
    let y = if m <= 2 { y + 1 } else { y };

    format!("{:04}-{:02}-{:02}", y, m, d)
}