Applying custom functions directly in GROQ for data destructuring from datetime.

*[_type == "open_course" && is_active == true]{ 
in_person{
  'year' : new Date(start_date).getFullYear()
   }
  }
 }

"year": string::split(start_date, '-')[0]

/**
 * @param {string | number | Date} date
 */
function formatTime(date) {
	var d = new Date(date),
		hours = '' + d.getHours(),
		minutes = '' + d.getMinutes();

	if (hours.length < 2) hours = '0' + hours;
	if (minutes.length < 2) minutes = '0' + minutes;

	return [hours, minutes].join(':');
}

/**
 * @param {string | number | Date} date
 */
function formatDateMonthName(date) {
	var d = new Date(date),
		month = '' + (d.getMonth() + 1),
		day = '' + d.getUTCDate(),
		year = d.getUTCFullYear();
	if (month.length < 2) month = '0' + month;
	if (day.length < 2) day = '0' + day;
	// @ts-ignore
	const monthStr = months[parseInt(month)];
	return `${monthStr} ${day}, ${year}`;
}