I've got log files that have timestamps specified in microseconds.
Example lines:

1570540970652: giveMacToRegistrant Giving mac 00:0d:05:07:23:f9 to Registrant Application PC
1570540970653: configureInterface Configuring interface eth1 (mac address 00:0d:05:07:23:f9) for Backpack communication.
1570540970653: ifcfg-eth1 modified. Bouncing the interface.

Our local timezone is GMT -4 (US Eastern), so that first time is 9:22:50.652 AM local, 1:22:50.652 PM GMT.

The filename is 2019-10-08_09-22-40.dump and my parser setting is thus:
File name patter: *.dump
PatternParser
%d{Elapsed}: %m%n

(I've also done it with %d: %m%n, no difference)

When I load this file I end up with the times displayed being in GMT.

I've tried playing with Settings->Application->Date & Time, but I can't get any other behavior, no matter how I specify the 'when time zone is unspecified' and 'convert timestamps to' settings.

How do I make these files come up correctly?

Alternately, is there a quick way to switch the offset for a given file? Or specify an offset for a file type in the parser mappings? Right now all I can do is switch to the File Tab, click the Time Offset button and type in an offset for the given file. Which works, but is a major pain in the neck when I've got twenty files that I need to do this for at once.