message: minor enhancement to DateTime
diff: @@ -213,12 +213,6 @@ DateTime::DateTime (DateType d,
  minute_ (mn),
  second_ (sc),
  nanosecond_ (ns),
  -
  - // Refer to the comment in the header file, as why we are assigning
  - // INVALID_TIME_T_ to time_.
  - //
  - time_ (INVALID_TIME_T_),
  - week_day_ (DT_WEEKDAY::BAD_DAY),
  time_zone_ (tz) {
  }
  @@ -241,9 +235,7 @@ DateTime::DateTime (DateType d,
  // (5) YYYY/MM/DD HH:MM:SS.MMM
  //
  DateTime::DateTime (const char *s, DT_DATE_STYLE ds, DT_TIME_ZONE tz)
  - : time_ (INVALID_TIME_T_),
  - week_day_ (DT_WEEKDAY::BAD_DAY),
  - time_zone_ (tz) {
  + : time_zone_ (tz) {
  const char *str = s;
  @@ -424,7 +416,7 @@ days_in_month_ (DT_MONTH month, DatePartType year) noexcept {
  //
  bool DateTime::is_valid () const noexcept {
  - return (year () > 1900 && year () < 2525 &&
  + return (year () > 0 && year () < 9999 &&
  month () > DT_MONTH::BAD_MONTH && month () <= DT_MONTH::DEC &&
  dmonth () > 0 &&
  dmonth () <= days_in_month_ (month(), year()) &&
  @@ -820,13 +812,11 @@ void DateTime::add_days (long days) noexcept {
  while (date () == prev_date.date ())
  add_seconds (3600 * addend);
  }
  - else if (addend > 0 &&
  - int(dyear ()) - int(prev_date.dyear ()) > 1) {
  + else if (addend > 0 && int(dyear()) - int(prev_date.dyear()) > 1) {
  while (int(dyear ()) - int(prev_date.dyear ()) > 1)
  add_seconds (-3600 * addend);
  }
  - else if (addend < 0 &&
  - int(dyear ()) - int(prev_date.dyear ()) < -1) {
  + else if (addend < 0 && int(dyear()) - int(prev_date.dyear()) < -1) {
  while (int(dyear ()) - int(prev_date.dyear()) < -1)
  add_seconds (3600);
  }
  