function getDateAsync(onSuccess, onFailure) {
   ...
}

function getValidDate() {
    return new Promise((resolve, reject) => {
       getDateAsync((date) => {
         checkValidDate(date, resolve, reject);
       }, () => {
         markDateInvalid();
         reject();
       }
    });
}

function checkValidDate(date, resolve, reject) {
   if (isValid(date)) {
      resolve(date);
   } else {
      markDateInvalid();
      reject();
   }
}

function markDateInvalid() { ... }