mysql - CONVERT_TZ not working -

we have script run through php myadmin, follows:

update utilities_alert set date=convert_tz(date,'-06:00','00:00'); update utilities_update set date=convert_tz(date,'-06:00','00:00'); update utilities_assetlocation set start=convert_tz(start,'-06:00','00:00'); update utilities_assetlocation set end=convert_tz(end,'-06:00','00:00'); update utilities_idlelog set date=convert_tz(date,'-06:00','00:00'); 

it's not working , returning null values. came across this

http://www.geeksengine.com/article/populate-time-zone-data-for-mysql.html

, followed steps , no avail.

there may bug in verb, spent time getting frustrated trying this. did work if used format.

select convert_tz(timeseen, 'america/new_york','europe/london'); 

where timeseen datetime field.

if have loaded timezone data say, should work.