/**
 * Calculates the number of days since a given date.
 *
 * @param {string} day_string - The start date in "YYYY-MM-DD" format.
 * @returns {number} The number of days since the start date.
 */
function days_since (day_string) {
	var start_date = moment(day_string, "YYYY-MM-DD");
	var today = moment();
	var duration = moment.duration(today.diff(start_date));
	var days_since = parseInt(duration.asDays());
	return days_since;

 } 
module.exports = days_since;