Function
function getFormatedStringFromDays(numberOfDays) {
var years = Math.floor(numberOfDays / 365);
var months = Math.floor(numberOfDays % 365 / 30);
var days = Math.floor(numberOfDays % 365 % 30);
return [years, months, days].join(':');
}
Usage
const str = getFormatedStringFromDays(400);
Result
1:1:5