parseTime

pub fn parseTime(cert: Certificate, elem: der.Element) ParseTimeError!u64 {
    const bytes = cert.contents(elem);
    switch (elem.identifier.tag) {
        .utc_time => {
            // Example: "YYMMDD000000Z"
            if (bytes.len != 13)
                return error.CertificateTimeInvalid;
            if (bytes[12] != 'Z')
                return error.CertificateTimeInvalid;

            return Date.toSeconds(.{
                .year = blk: {
                    const year = try parseTimeDigits(bytes[0..2], 0, 99);
                    break :blk if (year < 50) @as(u16, 2000) + year else @as(u16, 1900) + year;
                },
                .month = try parseTimeDigits(bytes[2..4], 1, 12),
                .day = try parseTimeDigits(bytes[4..6], 1, 31),
                .hour = try parseTimeDigits(bytes[6..8], 0, 23),
                .minute = try parseTimeDigits(bytes[8..10], 0, 59),
                .second = try parseTimeDigits(bytes[10..12], 0, 59),
            });
        },
        .generalized_time => {
            // Examples:
            // "19920521000000Z"
            // "19920622123421Z"
            // "19920722132100.3Z"
            if (bytes.len < 15)
                return error.CertificateTimeInvalid;
            return Date.toSeconds(.{
                .year = try parseYear4(bytes[0..4]),
                .month = try parseTimeDigits(bytes[4..6], 1, 12),
                .day = try parseTimeDigits(bytes[6..8], 1, 31),
                .hour = try parseTimeDigits(bytes[8..10], 0, 23),
                .minute = try parseTimeDigits(bytes[10..12], 0, 59),
                .second = try parseTimeDigits(bytes[12..14], 0, 59),
            });
        },
        else => return error.CertificateFieldHasWrongDataType,
    }
}