Using OData, update a DateTime field for an entity record. Set the field to the current date and time (with UTC offset)

// Sets a DateTime field's value to the current date/time and updates the record.
updateEntityFieldWithCurrentDateTime: function (entitySchemaName, entityGuid, dateTimeFieldSchemaName, successCallback, errorCallback) {
    // This is an example of getting the OData URI. See the CRM SDK for more info.
    var uri = getOdataUri();
    // Get the current date/time offset for the current time zone.
    // This is to store the current date/time to CRM in UTC (the local time minus the time zone offset).
    var now = new Date();
    var timeZoneOffsetHours = now.getTimezoneOffset() / 60;
    var d2 = new Date();
    d2.setHours(now.getHours() - timeZoneOffsetHours);
    var entityToUpdate = {};
    entityToUpdate[dateTimeFieldSchemaName] = d2;
    var jsonEntity = JSON.stringify(entityToUpdate);
        type: "POST",
        contentType: "application/json; charset=utf-8",
        datatype: "json",
        data: jsonEntity,
        url: uri + "/" + entitySchemaName + "Set(guid'" + entityGuid + "')",
        async: false,
        beforeSend: function (xmlhttp) {
            xmlhttp.setRequestHeader("Accept", "application/json");
            xmlhttp.setRequestHeader("X-HTTP-Method", "MERGE");
        success: successCallback,
        error: function (XmlHttpRequest, textStatus, errorThrown) {