Hello, @Rahul_Bansal! Welcome to the community!
You need to calculate your new date at your application level:
var dateToInsert = new Date(
Date.now() + 2 * 1000
);
db.test1.updateOne(
{
privateIp: '<ip>',
},
{
$set: {
updateTime: dateToInsert,
}
},
{
upsert: true,
}
);