Angular 1.x moment input directive with validators and formatters

MomentDateTimeDirective.js

function momentDateTime() {
        var format = "YYYY-MM-DD HH:mm"
        //date.isValid() is not enough for strict validation, see moment.js doc
        var pattern = /^\s*\d{4}-\d{2}-\d{2}\s+\d{2}:\d{2}(:\d{2})?\s*$/
        return {
            restrict: 'A',
            require: 'ngModel',
            link: function (scope, element, attr, ngModel) {
                ngModel.$parsers.push(function (text) {
                    var date = moment(text, format);
                    ngModel.$validators.dateValid = function(modelValue, viewValue) {
                        return modelValue.isValid() && pattern.test(viewValue);
                    }
                    return date;
                })
                ngModel.$formatters.push(function (datetime_moment) {
                    return datetime_moment && datetime_moment.local().format(format);
                })
            }
        };
    }