SELECT CONVERT_TZ() will work for that.but its not working for me.
Why, what error do you get?
SELECT CONVERT_TZ(displaytime,'GMT','MET');
should work if your column type is timestamp, or date
http://dev.mysql.com/doc/refman/5.0/en/date-and-time-functions.html#function_convert-tz
Test how this works:
SELECT CONVERT_TZ(a_ad_display.displaytime,'+00:00','+04:00');
Check your timezone-table
SELECT * FROM mysql.time_zone;
SELECT * FROM mysql.time_zone_name;
http://dev.mysql.com/doc/refman/5.5/en/time-zone-support.html
If those tables are empty, you have not initialized your timezone tables. According to link above you can use mysql_tzinfo_to_sql
program to load the Time Zone Tables. Please try this
shell> mysql_tzinfo_to_sql /usr/share/zoneinfo
or if not working read more: http://dev.mysql.com/doc/refman/5.5/en/mysql-tzinfo-to-sql.html