See https://developer.matomo.org/guides/persistence-and-the-mysql-backend

For further questions please ask in our forums https://forum.matomo.org/c/plugins-platform

Thanks a lot!
But what's the relationship between 'visit_first_action_time' and 'visitor_localtime'?
It seems visitor_localtime is ahead 8 hours of visit_first_action_time?

The 'visit_first_action_time' looks fine on the matomo web, but in database this time value seems is 8 hours ahead of real visit_first action_time.
such as :
on the matomo web: Mar 5, 2019 14:07:58
but in matomo database, in table matomo_log_visit I got this record is:
select idvisit, visitor_localtime, visit_first_action_time, visit_last_action_time from matomo_log_visit;
| 24535 | 14:09:23 | 2019-03-05 06:07:58 | 2019-03-05 06:08:27 |

It just 8 housr ahead of real visit_first_action_time.

visit_first_action_time is UTC, visitor_localtime is local time depending on users' timezone

Thank you the response!
I still can not understand well what's the relationship between 'visitor_localtime' and 'visit_first_action_time&& visit_last_action_time', it seems visitor_localtime is several
minutes later after visit_last_action_time. Is there some relationship?

there is no relationship

Why need visitor_localtime?

the local user time report uses it

Does it stand for just visitor's local time or stands for one visit time base of visitor's local time zone?

visitor's local time not in the visitors local time zone