anchor.diff:    /// of whether the time is in UTC or in the local time zone.
     ///
     /// ```dart
  -  /// var now = DateTime.now();
  -  /// var later = now.add(const Duration(seconds: 5));
  -  /// assert(later.isAfter(now));
  -  /// assert(!now.isBefore(now));
  +  /// final now = DateTime.now();
  +  /// final later = now.add(const Duration(seconds: 5));
  +  /// print(later.isAfter(now)); // true
  +  /// print(!now.isBefore(now)); // true
     ///
     /// // This relation stays the same, even when changing timezones.
  -  /// assert(later.isAfter(now.toUtc()));
  -  /// assert(later.toUtc().isAfter(now));
  -  ///
  -  /// assert(!now.toUtc().isAfter(now));
  -  /// assert(!now.isAfter(now.toUtc()));
  +  /// print(later.isAfter(now.toUtc())); // true
  +  /// print(later.toUtc().isAfter(now)); // true
  +  ///
  +  /// print(!now.toUtc().isAfter(now)); // true
  +  /// print(!now.isAfter(now.toUtc())); // true
     /// ```
     external bool isAfter(DateTime other);
   
  
positive.code:   /// local time zone.
    ///
    /// ```dart
    /// var thisInstant = DateTime.now();
    /// ```
    DateTime.now() : this._now();
  
  
negative.code:   /// time zone.
    ///
    /// ```dart
    /// final now = DateTime.now();
    /// final later = now.add(const Duration(seconds: 5));
    /// print(!later.isAtSameMomentAs(now)); // true
    /// print(now.isAtSameMomentAs(now)); // true
    ///
    /// // This relation stays the same, even when changing timezones.
    /// print(!later.isAtSameMomentAs(now.toUtc())); // true
    /// print(!later.toUtc().isAtSameMomentAs(now)); // true
    ///
    /// print(now.toUtc().isAtSameMomentAs(now)); // true
    /// print(now.isAtSameMomentAs(now.toUtc())); // true
    /// ```
    external bool isAtSameMomentAs(DateTime other);
  
    /// Compares this DateTime object to [other],
    /// returning zero if the values are equal.
    ///
    /// A [compareTo] function returns:
    ///  * a negative value if this DateTime [isBefore] [other].
    ///  * `0` if this DateTime [isAtSameMomentAs] [other], and
    ///  * a positive value otherwise (when this DateTime [isAfter] [other]).
    ///
    /// ```dart
    /// final now = DateTime.now();
    /// final future = now.add(const Duration(days: 2));
    /// final past = now.subtract(const Duration(days: 2));
    /// final newDate = now.toUtc();
    ///
    /// print(now.compareTo(future)); // -1
    /// print(now.compareTo(past)); // 1
    /// print(now.compareTo(newDate)); // 0
    /// ```
    external int compareTo(DateTime other);
  
    int get hashCode => (_value ^ (_value >> 30)) & 0x3FFFFFFF;
  