DateTime to int

main.dart

int dateToValue(DateTime date) {
  assert(date.isUtc, 'DateTime must be in UTC');
  return (date.year << 9) | (date.month << 5) | date.day;
}

DateTime valueToDate(int value) =>
    DateTime.utc(value >> 9, (value >> 5) & 0xF, value & 0x1F);

int dateTimeToValue(DateTime dateTime) {
  assert(dateTime.isUtc, 'DateTime must be in UTC');
  return (dateTime.year << 26) |
      (dateTime.month << 22) | // MMMM (1–12)
      (dateTime.day << 17) | // DDDDD (1–31)
      (dateTime.hour << 12) | // HHHHH (0–23)
      (dateTime.minute << 6) | // MMMMMM (0–59)
      dateTime.second; // SSSSSS (0–59)
}

DateTime valueToDateTime(int value) => DateTime.utc(
  value >> 26, // Год
  (value >> 22) & 0xF, // Месяц (4 бита)
  (value >> 17) & 0x1F, // День (5 бит)
  (value >> 12) & 0x1F, // Часы (5 бит)
  (value >> 6) & 0x3F, // Минуты (6 бит)
  value & 0x3F, // Секунды (6 бит)
);

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(2021, 1, 1, 1, 1, 1),
    DateTime.utc(2024, 10, 10, 10, 10, 10),
    DateTime.utc(-10, 10, 10, 10, 10, 10),
    DateTime.utc(3000, 12, 30, 23, 59, 59),
  ];

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

    // Проверка конвертации даты
    expect(valueToDate(dateToValue(date)), date);

    // Проверка конвертации даты и времени
    expect(valueToDateTime(dateTimeToValue(dt)), dt);

    // Проверка компактности
    final DateTime(:year, :month, :day, :hour, :minute, :second) = dt;
    final text = [
      year,
      month,
      day,
      hour,
      minute,
      second,
    ].map((e) => e.toString().padLeft(2, '0')).join('');
    if (text.length < dateTimeToValue(dt).toString().length) {
      throw Exception('$text is more compact than ${dateTimeToValue(dt)}');
    }
  }

  // 5 Mar. 2025 12:34:56
  // ignore: avoid_print
  print(dateTimeToValue(DateTime.utc(2025, 03, 05, 12, 34, 56)));
}