Unix epoch time is the amount of seconds elapsed since 00:00:00 1st January 1970. Even more interesting is in 2038 the count will go to negative as it will reach maximum size for a 32-bit integer.
Unix epoch time format is completely unreadable to humans, it looks like this: 1565789147. You simply cannot figure out the year, month, day, hour, minute or seconds from that.
To convert it into something more readable or standard for database storage declare a new DateTime using the Unix epoch time and then convert its fomat into the style of your choice.
<?php $epoch_time = 1565789147; $date_time = new DateTime("@$epoch_time"); echo $date_time->format('Y-m-d H:i:s');//2019-08-14 13:25:47
You can see all the format parameters here.