@timestamp always 8h exact more than the matching time?

Elastic Stack Logstash
1

Hi I know there are quite a few topics on this. But still i couldn't figure it out after reviewing them.

THIS is how i date filtered date field to target @timestamp (tried with and without timezone).

date{
match => ["date", "YYYY-MM-dd HH:mm:ss", "ISO8601" ]
timezone => "US/Pacific"
target => "@timestamp"
}

HOWEVER, when I parsed it, @timestamp is exactly 8hours ahead of date field.
{
"@timestamp" => "2016-01-01T07:02:14.000Z",
"app_id" => "as",
"date" => "2015-12-31 23:02:14",
"member_id" => 25241916,
"locale" => "en_US",
"p_source" => "web",
"p_typeId" => 2,
"p_contentId" => 98060092
}

Would you have any ideas of why?

2

When i change the timezone to Ireland (Europe Dublin), it got right between @timestamp and date field. I know that our server is in Ireland, so maybe thats why. But how can Logstash recognize it??

Got right when i set timezone to Europe/Dublin
{
"@timestamp" => "2015-12-31T23:02:14.000Z",
"app_id" => "as",
"date" => "2015-12-31 23:02:14",
"member_id" => 25241916,
"locale" => "en_US",
"p_source" => "web",
"p_typeId" => 2,
"p_contentId" => 98060092
}

3

Got it. Elastic uses UTC by default. And we are suggested not to change it.