All dates should be in UTC time

[php-coder]

We should store dates in UTC time and convert to user's timezone when needed.

[php-coder]

When this ticket will be done we should also update SitemapController and remove hard-coded server's time (were introduced in e15f227 commit and related to #66).

[php-coder]

May be useful: http://www.baeldung.com/reddit-app-show-date-in-the-users-timezone

[php-coder]

May be useful: https://vladmihalcea.com/2017/03/14/how-to-store-date-time-and-timestamps-in-utc-time-zone-with-jdbc-and-hibernate/

[php-coder]

May be useful: https://vladmihalcea.com/2017/03/14/how-to-store-date-time-and-timestamps-in-utc-time-zone-with-jdbc-and-hibernate/

It's really useful. Perhaps, we should set useLegacyDatetimeCode=false