Javascript 如何使用MongoDB计算和更新NodeJS服务器上的实时日期/时间

我在MongoDB中有这样的“发货”数据

{   "_id": {
        "$oid": "60aff39872c1b74891b254b8"
    },
    "track": [],
    "packageId": "00001",
    "currentLocation": "currentLocation",
    "destination": "destination",
    "origin": "XYZ CITY",
    "bagsCount": 16,
    "modeofTransport": "Air",
    "createdBy": "abcd WarehouseAgent",
    "handoverTo": {
        "userId": {
            "$oid": "60aaa09a3b985f3794738280"
        }
    },
    "status": "Waiting For Verification",

    "eta":???   //(Amount of time shipment will use to reach DESTINATION)
                // how do I get "Eta" from the user and in which Format
    
}

问题

• 如何从用户处获取“eta”以及以何种格式（日期/时间）

• NodeJs服务器如何根据实际时间不断更新每个包的“eta”