The update time is sent to Whzan if either of two conditions are met, the first is if there is something to send to whzan anyway, the second being if the gateway has not sent anything for more than 5 minutes. This allows you in the mimic to test this time and detect if the gateway has not updated whzan for a long time, normally an indication of a connection issue.
The date time value sent to Whzan is the time of the Whzan server and so is in Universal time. You can test it against #UtcNow to see how long ago the gateway sent data to Whzan. To get in local time you'll need to add one hour to the time.
We should have a function to translate this to local time for you, I'll enter it into our task list.