Javascript – Resolving Moment.js Deprecation Warning in Angular App

I am getting an warning for the following code, using moment.js, in my Angular app:

moment(value).add(6, 'hours').format("MM/DD/YYYY");

The warning/error printing to the console is:

moment.js:293 Deprecation warning: value provided is not in a
recognized RFC2822 or ISO format. moment construction falls back to js
Date(), which is not reliable across all browsers and versions. Non
RFC2822/ISO date formats are discouraged and will be removed in an
upcoming major release. Please refer to
http://momentjs.com/guides/#/warnings/js-date/ for more info.
Arguments: [0] _isAMomentObject: true, _isUTC: false, _useUTC: false,
_l: undefined, _i: Apr 10, 2007, 10:00:00 PM, _f: undefined, _strict: undefined, _locale: [object Object]

I have looked at the documentation page linked in the warning, but it's still unclear to me what I need to change to get rid of the deprecation warning. I tried, for instance, adding an empty array as a second argument:

moment(value, []).add(6, 'hours').format("MM/DD/YYYY");

…but while that gets rids of the error, I get "invalid date" printed in my view, instead of the actual date. How do I need to adjust the syntax here to get rid of the warning?

UPDATE: The value being provided is a UTC value that has been transformed using the Angular date pipe. So I am passing through two pipes: first the Angular date pipe, and then this custom pipe using moment. the full pipe code looks like this:

import { Pipe, PipeTransform } from '@angular/core';
const moment = require('moment');

@Pipe({name: 'timeZoneSync'})
export class TimeZoneSyncPipe implements PipeTransform {

    constructor() { }

    transform(value) {
        if (value) {
            return moment(value).add(6, 'hours').format("MM/DD/YYYY");
        }
    }
}

And in my view I am using the two pipes like this:

  <input class="app-input" [ngModel]="client.dob | timeZoneSync | date:'medium'"
                                (ngModelChange)="client.dob=$event" name="inputField" type="text" />