ZonedDateTime.fromDateTime constructor

ZonedDateTime.fromDateTime(
  1. DateTime dateTime, [
  2. ZoneId? zone
])

Creates a ZonedDateTime from a standard DateTime object.

The DateTime is assumed to be in the specified timezone. If no timezone is provided, it defaults to UTC.

Example:

final dateTime = DateTime(2023, 12, 25, 15, 30);
final zonedUtc = ZonedDateTime.fromDateTime(dateTime); // Assumes UTC
final zonedEst = ZonedDateTime.fromDateTime(dateTime, ZoneId.of('EST'));

print('As UTC: $zonedUtc');
print('As EST: $zonedEst');

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.fromDateTime(DateTime dateTime, [ZoneId? zone]) {
  zone ??= ZoneId.UTC;
  final localDateTime = LocalDateTime.fromDateTime(dateTime);
  return ZonedDateTime.of(localDateTime, zone);
}