# ZonedDateTime.now constructor

ZonedDateTime.now([

1. ZoneId? zone

])

Creates a ZonedDateTime from the current date and time in the specified timezone.

If no `zone` is provided, uses the system default timezone (UTC).

Example:

    final nowUtc = ZonedDateTime.now(); // Current time in UTC
    final nowLocal = ZonedDateTime.now(ZoneId.systemDefault());
    final nowTokyo = ZonedDateTime.now(ZoneId.of('Asia/Tokyo'));

    print('UTC: $nowUtc');
    print('Local: $nowLocal');
    print('Tokyo: $nowTokyo');

Represents a date-time with timezone information.

This class combines a LocalDateTime with timezone information to represent a complete date-time with offset from UTC. Unlike Java's implementation, this version includes a built-in timezone database for common timezones without requiring external dependencies.

## Key Features:

- Immutable: All operations return new instances
- Timezone Aware: Handles UTC offsets and common timezone names
- DST Support: Basic daylight saving time handling for major timezones
- Conversion: Easy conversion between timezones
- Formatting: ISO 8601 compliant string representation

## Supported Timezone Formats:

- UTC Offsets: `+05:00`, `-08:00`, `Z` (for UTC)
- Timezone Names: `EST`, `PST`, `GMT`, `CET`, etc.
- Full Names: `America/New_York`, `Europe/London`, etc.

## Usage Examples:

    // Create from current time
    final now = ZonedDateTime.now();
    final nowInParis = ZonedDateTime.now(ZoneId.of('Europe/Paris'));

    // Create with specific date-time
    final localDT = LocalDateTime.of(2023, 12, 25, 15, 30);
    final christmas = ZonedDateTime.of(localDT, ZoneId.of('America/New_York'));

    // Parse from string
    final parsed = ZonedDateTime.parse('2023-12-25T15:30:00+01:00[Europe/Paris]');

    // Convert between timezones
    final utc = christmas.toUtc();
    final tokyo = christmas.withZoneSameInstant(ZoneId.of('Asia/Tokyo'));

    // Arithmetic operations
    final tomorrow = christmas.plusDays(1);
    final nextHour = christmas.plusHours(1);

## Timezone Database:

This implementation includes a comprehensive timezone database with:

- Major world timezones with their UTC offsets
- Daylight saving time rules for common timezones
- Historical timezone data for accurate conversions
- Support for both abbreviated and full timezone names

## Implementation

    factory ZonedDateTime.now([ZoneId? zone]) {
      zone ??= ZoneId.UTC;
      final utcNow = DateTime.now().toUtc();
      final localDateTime = LocalDateTime.fromDateTime(utcNow);

      if (zone == ZoneId.UTC) {
        return ZonedDateTime._(localDateTime, zone, Duration.zero, false);
      }

      // Convert UTC to the target timezone
      final offsetData = TimezoneDatabase.getOffsetForZone(zone.id, localDateTime);
      final adjustedDateTime = localDateTime.plus(offsetData.offset);

      return ZonedDateTime._(adjustedDateTime, zone, offsetData.offset, offsetData.isDst);
    }