postgres with timezone for drupal 6

Hello

I want to create a finish_time field as timestamp with timezone

In Drupal 5, I can create a timestamp field using "CREATE TABLE myTable (finish_time timestamptz NOT NULL DEFAULT current_timestamp,.....".

In Drupal 6, I try to use the following:

'finish_time'=> array( 'type' => 'datetime' , 'not null' => TRUE, 'default' =>'now()')

However, the created field type is "timestamp without time zone".

I tried :

'finish_time'=> array( 'type' => 'timestamptz' , 'not null' => TRUE, 'default' =>'now()')

But it does not work.

My question is how I can create this finish_time with "timestamp with time zone".

Many thanks
john