Update the Calendar by sql script

Friends,

Each Year at thanksgiving (USA date) we switch over from our regular programming to a Christmas focussed one, which will run till Three Kings (Jan 06).
This is a huge job using the calendar functions.

We would love to do this by running an SQL query against the Postgress Db.
Has anyone experience on which tables are touched to set this up?
Has this been done before?
What sequence does LT use to create an entry?

thoughts??

Thanks for your feedback,
Chris.