I'm using Solr-6.2.1 on windows.
When setting set SOLR_TIMEZONE=PST, in solr.in.cmd file, dataimport.properties file saves last_index_time in PDT i.e. UTC-07:00.
When setting set SOLR_TIMEZONE=EST, in solr.in.cmd file, dataimport.properties file saves last_index_time in EST i.e. UTC-05:00.
But
When setting set SOLR_TIMEZONE=PDT or set SOLR_TIMEZONE=EDT, in solr.in.cmd file, dataimport.properties file saves last_index_time of the Server's TimeZone.
I didn't understand why Solr is saving Daylight for PST and not for EST. and why for PDT and EDT it shows time with regarding to the server.
Don't use EST and PST. They are there for backwards compatibility reasons. Instead prefer the ones marked "Canonical" in the list here. For example:
Instead of EST, for most locations using Eastern Time in the US, use America/New_York, or if in Canada use America/Toronto
Instead of PST, for most locations using Pacific Time in the US, use America/Los_Angeles, or if in Canada use America/Vancouver
Using these will allow your software to properly choose standard time or daylight time, depending on the date and time in question.