Function zonedWallClockToUtc

apps/sim/lib/core/utils/timezone.ts:160–173

(wallClock: string, timeZone: string)

 * calendar apps treat that once-a-year hour.
 */
export function zonedWallClockToUtc(wallClock: string, timeZone: string): Date {
  const [datePart, timePart] = wallClock.split('T')
  const [year, month, day] = datePart.split('-').map(Number)
  const [hour, minute, second = 0] = timePart.split(':').map(Number)
  const utcGuess = Date.UTC(year, month - 1, day, hour, minute, second)
  const guessOffset = timezoneOffsetMs(new Date(utcGuess), timeZone)
  const candidate = utcGuess - guessOffset
  const candidateOffset = timezoneOffsetMs(new Date(candidate), timeZone)
  if (candidateOffset === guessOffset) return new Date(candidate)
  const adjusted = utcGuess - candidateOffset
  return timezoneOffsetMs(new Date(adjusted), timeZone) === candidateOffset
    ? new Date(adjusted)
    : new Date(candidate)
}