DateTime to int, Date and Time extension

main.dart

// ignore_for_file: avoid_print

/*
 * Date <==> Int conversion
 * https://gist.github.com/PlugFox/a94be8655b2adb91336f03bc77513d76
 * https://dartpad.dev?id=a94be8655b2adb91336f03bc77513d76
 * Mike Matiunin <[email protected]>, 20 March 2025
 */

/// Date extension type
extension type const Date._(DateTime _date) implements DateTime {
  /// Create Date from [year], [month] and [day]
  Date(int year, int month, int day) : _date = DateTime.utc(year, month, day);

  /// Get current Date
  factory Date.now() => Date.of(DateTime.now());

  /// Create Date from [date]
  factory Date.of(DateTime date) {
    final DateTime(:year, :month, :day) = date.toUtc();
    return Date(year, month, day);
  }

  /// Create Date from [value]
  Date.value(int value)
    : _date = DateTime.utc(
        value >> 9, // year (12 bit)
        (value >> 5) & 0xF, // month (4 bit)
        value & 0x1F, // day (5 bit)
      );

  /// Get Date as value
  int get value =>
      (_date.year << 9) | // YYYYYYYYYYYY (0–4095)
      (_date.month << 5) | // MMMM (1–12)
      _date.day; // DDDDD (1–31)

  /// Get Date as representation YYYY-MM-DD
  String get representation =>
      '${year.toString().padLeft(4, '0')}-'
      '${month.toString().padLeft(2, '0')}-'
      '${day.toString().padLeft(2, '0')}';
}

/// Time extension type
extension type const Time._(DateTime _time) implements DateTime {
  /// Create Time from [hour], [minute] and [second]
  Time(int hour, int minute, int second)
    : _time = DateTime.utc(0, 1, 1, hour, minute, second);

  /// Get current time
  factory Time.now() => Time.of(DateTime.now());

  /// Create Time from [time]
  factory Time.of(DateTime time) {
    final DateTime(:hour, :minute, :second) = time.toUtc();
    return Time(second, minute, second);
  }

  /// Create Date from [value]
  Time.value(int value)
    : _time = DateTime.utc(
        0,
        1,
        1,
        (value >> 12) & 0x1F, // Hours (5 bit)
        (value >> 6) & 0x3F, // Minutes (6 bit)
        value & 0x3F, // Seconds (6 bit)
      );

  /// Get Time as value
  int get value =>
      (_time.hour << 12) | // HHHHH (0–23)
      (_time.minute << 6) | // MMMMMM (0–59)
      _time.second; // SSSSSS (0–59)

  /// Get Date as representation HH:MM:SS
  String get representation =>
      '${hour.toString().padLeft(2, '0')}:'
      '${minute.toString().padLeft(2, '0')}:'
      '${second.toString().padLeft(2, '0')}';
}

void main() {
  void expect(DateTime a, DateTime b) {
    final $a = a.millisecondsSinceEpoch, $b = b.millisecondsSinceEpoch;
    if ($a == $b) return;
    throw Exception('${a.toUtc()} != ${b.toUtc()}');
  }

  final dates = [
    DateTime.utc(0),
    DateTime.utc(2021, 1, 1),
    DateTime.utc(2024, 10, 10),
    DateTime.utc(5000, 12, 30),
  ];

  for (final dt in dates) {
    final date = DateTime.utc(dt.year, dt.month, dt.day);

    // Check conversion date to value and back
    expect(Date.value(Date.of(date).value), date);

    print('$date => ${Date.of(dt).value}');

    // Check how compact is the value
    final DateTime(:year, :month, :day) = dt;
    final text = [
      year,
      month,
      day,
    ].map((e) => e.toString().padLeft(2, '0')).join('');
    if (text.length < Date.of(dt).value.toString().length) {
      throw Exception('$text is more compact than ${Date.of(dt).value}');
    }
  }

  // 5 Mar. 2025
  print(Date.of(DateTime.utc(2025, 03, 05)).value); // 1036901
  print(Date.value(1036901).representation); // 5 Mar. 2025

  // 12:34:56
  print(Time.of(DateTime.utc(0, 0, 0, 12, 34, 56)).value); // 51384
  print(Time.value(51384).representation); // 12:34:56
}

problem with years in web

problem with years in web

I'll take a look

@arxdeus it's unsafe to use conversion to DateTime with seconds at web.
Because its int limited to value 2^53 – 1.
We should not include seconds in that conversion or store time separately from the date.