convertTimeForLocale

gistfile1.txt

function convertTimeForLocale(timeString, currentTimezone, targetTimezone) {
  // Check if time starts with ~
  if (!timeString.startsWith('~')) {
    return timeString; // Return as-is if no ~ prefix
  }
  
  // If same timezone, return as-is
  if (currentTimezone === targetTimezone) {
    return timeString;
  }
  
  // Extract time (remove ~)
  const timeOnly = timeString.substring(1);
  
  // Parse time
  const [time, period] = timeOnly.includes('am') || timeOnly.includes('pm') 
    ? [timeOnly.replace(/[ap]m/i, '').trim(), timeOnly.match(/[ap]m/i)?.[0]]
    : [timeOnly, null];
  
  const [hours, minutes] = time.split(/[:.]/);
  let hour24 = parseInt(hours);
  
  // Convert to 24-hour format if needed
  if (period) {
    if (period.toLowerCase() === 'pm' && hour24 !== 12) hour24 += 12;
    if (period.toLowerCase() === 'am' && hour24 === 12) hour24 = 0;
  }
  
  // Create a date object for today with the given time
  const today = new Date();
  const currentTime = new Date(today.getFullYear(), today.getMonth(), today.getDate(), hour24, parseInt(minutes) || 0);
  
  // Get time in current timezone as string, then parse in target timezone
  const timeInCurrent = currentTime.toLocaleString('en-CA', {
    timeZone: currentTimezone,
    year: 'numeric',
    month: '2-digit',
    day: '2-digit',
    hour: '2-digit',
    minute: '2-digit',
    second: '2-digit',
    hour12: false
  });
  
  // Create new date from the current timezone time
  const sourceDate = new Date(timeInCurrent);
  
  // Convert to target timezone
  const targetTime = sourceDate.toLocaleTimeString('en-US', {
    timeZone: targetTimezone,
    hour: 'numeric',
    minute: '2-digit',
    hour12: true
  });
  
  return `~${targetTime}`;
}

// Usage examples:
console.log(convertTimeForLocale('~9:30pm', 'Asia/Singapore', 'Asia/Kolkata')); // Singapore to India
console.log(convertTimeForLocale('~7:00pm', 'Asia/Kolkata', 'Asia/Singapore')); // India to Singapore
console.log(convertTimeForLocale('~9:30pm', 'Asia/Singapore', 'Asia/Singapore')); // Same timezone
console.log(convertTimeForLocale('meet at 5pm', 'Asia/Singapore', 'Asia/Kolkata')); // No ~ prefix