Daylight Saving Time & Timezone Converter

// Convert a meeting time into target location's wall-clock time
function formatInTimezone(date: Date, timeZone: string): string {
  return new Intl.DateTimeFormat('en-US', {
    timeZone,
    dateStyle: 'full',
    timeStyle: 'long',
    hourCycle: 'h23',
  }).format(date);
}

// Check if a timezone is currently observing Daylight Saving Time
function isTimezoneInDST(timeZone: string, date = new Date()): boolean {
  const year = date.getFullYear();
  const getOffset = (d: Date) => {
    const parts = new Intl.DateTimeFormat('en-US', {
      timeZone,
      hourCycle: 'h23',
      year: 'numeric', month: 'numeric', day: 'numeric',
      hour: 'numeric', minute: 'numeric', second: 'numeric'
    }).formatToParts(d);
    const p: Record<string, number> = {};
    parts.forEach(pt => { if (pt.type !== 'literal') p[pt.type] = parseInt(pt.value, 10); });
    return Date.UTC(p.year, p.month - 1, p.day, p.hour === 24 ? 0 : p.hour, p.minute, p.second) - d.getTime();
  };

  const janOffset = getOffset(new Date(Date.UTC(year, 0, 15)));
  const julOffset = getOffset(new Date(Date.UTC(year, 6, 15)));
  const currentOffset = getOffset(date);

  return currentOffset === Math.max(janOffset, julOffset) && janOffset !== julOffset;
}

from datetime import datetime
from zoneinfo import ZoneInfo

# Construct local meeting time in New York
ny_tz = ZoneInfo("America/New_York")
london_tz = ZoneInfo("Europe/London")
tokyo_tz = ZoneInfo("Asia/Tokyo")

# Define scheduled standup: November 2, 2026 at 10:00 AM NY time
meeting_ny = datetime(2026, 11, 2, 10, 0, tzinfo=ny_tz)

# Convert to attendee wall-clock times
meeting_london = meeting_ny.astimezone(london_tz)
meeting_tokyo = meeting_ny.astimezone(tokyo_tz)

print("NY Time:     ", meeting_ny.strftime("%Y-%m-%d %H:%M %Z (UTC%z)"))
print("London Time: ", meeting_london.strftime("%Y-%m-%d %H:%M %Z (UTC%z)"))
print("Tokyo Time:  ", meeting_tokyo.strftime("%Y-%m-%d %H:%M %Z (UTC%z)"))
# DST flag check
print("Is NY in DST:", bool(meeting_ny.dst()))

package main

import (
	"fmt"
	"time"
)

func main() {
	// Load standard IANA locations
	locNY, _ := time.LoadLocation("America/New_York")
	locLondon, _ := time.LoadLocation("Europe/London")

	// Meeting date during autumn desync window (Oct 28, 2026)
	meetingTime := time.Date(2026, 10, 28, 14, 0, 0, 0, locNY)

	// Evaluate in London
	londonTime := meetingTime.In(locLondon)

	zoneName, offsetSec := meetingTime.Zone()
	fmt.Printf("NY: %s (%s, UTC%+d)
", meetingTime.Format(time.RFC3339), zoneName, offsetSec/3600)
	
	lName, lOffset := londonTime.Zone()
	fmt.Printf("London: %s (%s, UTC%+d)
", londonTime.Format(time.RFC3339), lName, lOffset/3600)
}

-- Convert UTC timestamp column to user's wall-clock time
SELECT 
  event_id,
  created_at AT TIME ZONE 'UTC' AS utc_time,
  created_at AT TIME ZONE 'America/New_York' AS ny_local_time,
  created_at AT TIME ZONE 'Europe/London' AS london_local_time
FROM audit_logs
WHERE created_at >= '2026-10-01 00:00:00Z'
LIMIT 10;

-- Evaluate whether a specific timestamp observes daylight saving
SELECT 
  timezone('America/New_York', now()) AS wall_clock,
  EXTRACT(timezone FROM now() AT TIME ZONE 'America/New_York') / 3600 AS current_offset_hours;