help fixing my data if possible

The exact way to fix this will depend on what kind of date you are using, and whether or not you have dates that use different offsets (like when some are before and others after a change in daylight savings time), and what kind of timezone handling you are using.

Almost anything I can think of would be fairly complicated to do in SQL. I think it would be easier to write a small custom PHP script like the following. You'll have to play around with it to see exactly what gives you the right results:

$result = db_query("SELECT nid FROM {TABLE} ORDER BY nid");
while ($row = db_fetch_array($result)) {
  $node = node_load($row['nid']);
  $date = date_make_date($node->FIELD_NAME[0], DB_TIMEZONE, DATETYPE);
  date_modify($date, '+7 hours'); // Or whatever adjustment you find is needed.
  node_save($node);
}

Where
- TABLE is the table where your date data is stored,
- FIELD_NAME is the name of your field,
- DATETYPE is the type of date, 'date', 'datestamp' or 'datetime',
- DB_TIMEZONE is the timezone the data got stored as originally (UTC if you're using the site timezone, that bad timezone if you're using no timezone handling)

And then empty the cache_content table after you finish doing this or you'll keep seeing the old, cached values of the nodes.

I see I missed a step above. I created a date but didn't update the node value. You'll need to update $node->FIELD_NAME[0]['value'] and $node->FIELD_NAME[0]['value2'] with the new date before saving the node.