Рассчитать дни между датами
let startDate = "2021-04-01";
let date1 = new Date();
let date2 = new Date(startDate);
let timeInMilisec = date1.getTime() - date2.getTime();
let daysBetweenDates = Math.ceil(timeInMilisec / (1000 * 60 * 60 * 24));
D@RK$T@R