Shows how to work with dates by using the Moment JavaScript library with the Moment-MSDate plug-in.

Working with dates.EXCEL.yaml

name: Working with dates
description: >-
  Shows how to work with dates by using the Moment JavaScript library with the
  Moment-MSDate plug-in.
host: EXCEL
api_set: {}
script:
  content: |
    declare var moment: any;

    $("#setup").click(() => tryCatch(setup));
    $("#get-date-value").click(() => tryCatch(getDateValue));


    async function getDateValue() {
      await Excel.run(async (context) => {
        const sheet = context.workbook.worksheets.getItem("Sample");

        const dateRange = sheet.getRange("A2");
        dateRange.load("values");

        await context.sync();

        const nowMS = dateRange.values[0][0];

        console.log(`get (MSDate): ${nowMS}`);

        const nowMoment = moment.fromOADate(nowMS);
        console.log(`get (moment): ${JSON.stringify(nowMoment)}`);

        const now = nowMoment.unix();
        console.log(`get (timestamp): ${now}`);
      });
    }

    async function setup() {
      await Excel.run(async (context) => {
        context.workbook.worksheets.getItemOrNullObject("Sample").delete();
        const sheet = context.workbook.worksheets.add("Sample");
        const table = sheet.tables.add("A1:A6", true);

        table.getHeaderRowRange().values = [["Dates"]];
        const dateRange2 = sheet.getRange("A2:A6");
        dateRange2.numberFormat = [["dd/mm/yyyy;@"]];
        context.workbook.application.calculate(Excel.CalculationType.recalculate);
        await context.sync();
        table.rows.add(0, [["14/02/2020"], ["15/02/2020"], ["16/02/2020"], ["17/02/2020"], ["18/02/2020"]]);
        sheet.activate();
        await context.sync();
      });
    }

    /** Default helper for invoking an action and handling errors. */
    async function tryCatch(callback) {
      try {
        await callback();
      } catch (error) {
        // Note: In a production add-in, you'd want to notify the user through your add-in's UI.
        console.error(error);
      }
    }
  language: typescript
template:
  content: |
    <section class="ms-font-m">
        <p>Demo of issue with column formating with dates</p>
    </section>

    <section class="setup ms-font-m">
        <h3>Set up</h3>
        <button id="setup" class="ms-Button">
            <span class="ms-Button-label">Add sample data</span>
        </button>
    </section>

    <section class="samples ms-font-m">
        <h3>Try it out</h3>
        <button id="get-date-value" class="ms-Button">
            <span class="ms-Button-label">Get date value</span>
        </button>
    </section>
  language: html
style:
  content: |
    section.samples {
        margin-top: 20px;
    }

    section.samples .ms-Button, section.setup .ms-Button {
        display: block;
        margin-bottom: 5px;
        margin-left: 20px;
        min-width: 80px;
    }
  language: css
libraries: |
  https://appsforoffice.microsoft.com/lib/1/hosted/office.js
  @types/office-js

  office-ui-fabric-js@1.4.0/dist/css/fabric.min.css
  office-ui-fabric-js@1.4.0/dist/css/fabric.components.min.css

  core-js@2.4.1/client/core.min.js
  @types/core-js

  jquery@3.1.1
  @types/jquery@3.3.1

  moment@2.18.1 
  moment-msdate@0.2.2