log4j2 Json Layout

[Thome, Jerry]

We're using Vert.x and graduated from using JUL to log4j2.  Speed and 
functionality are great.

Is there information on the choice to represent the timestamp via "instant" as 
shown below?  It's hard to know what that time represents at a glance.

...
  "endOfBatch" : false,
  "loggerFqcn" : "io.vertx.core.logging.Logger",
  "instant" : {
    "epochSecond" : 1548267755,
    "nanoOfSecond" : 66000000
  },
  "threadId" : 20,
  "threadPriority" : 5,
  "source" : {
...

As there seem to be very few formatting options with the Json Layout, do users 
tend to customize the entire layout to represent the timestamp in a different 
format?

Thanks,
Jerry