chrono::duration::MINUnstable

pub const MIN: Duration = Duration{secs: i64::MIN / MILLIS_PER_SEC - 1,
         nanos:
             NANOS_PER_SEC +
                 (i64::MIN % MILLIS_PER_SEC) as i32 * NANOS_PER_MILLI,}

The minimum possible Duration: i64::MIN milliseconds.