如何通过在javascript中的expiry_time来检查令牌的到期时间

I am getting an access token from Flipkart API and gives me token with its expiry time . But i don't know what they given in expiry time they are giving some kind of timestamp in seconds, as i convert those seconds into minutes then there are 56 days like something that is coming. As i read the doc for that they said that token is expired after 60 days. But as i hit the API it will giving me different different time-stamp in expiry_time field each time. For example first timme it will give:-I am getting an access token from Flipkart API