Here are the relevant rules according to the 02/03 DCI M:TG Floor Rules(03/04 Floor rules have not been released):
104. New Releases
The following card sets are scheduled to release during the 2002–2003 tournament season: Onslaught™, Legions™, and the second small expansion of the Onslaught block.
They become legal in Constructed on the following days:
· Onslaught November 1, 2002
· Legions March 1, 2003
· Second small expansion
of Onslaught block July 1, 2003
These dates are subject to change. Any changes will be announced via an official DCI announcement that can be found at thedci.com.
New card sets are allowed in Limited play as soon as they’re released, including before their public releases in the case of Prerelease tournaments. For updates, please check thedci.com.
125. Standard-Format Deck Construction
The following card sets are permitted in Standard tournaments:
· Seventh Edition™
· Invasion™ (until October 31, 2002)
· Planeshift™ (until October 31, 2002)
· Apocalypse™ (until October 31, 2002)
· Odyssey™
· Torment™
· Judgment ™
· Onslaught (effective November 1, 2002)
· Legions (effective March 1, 2003)
· Second small expansion in Onslaught block (effective July 1, 2003)
Card sets rotate into the Standard environment on the specific dates noted in section 104. Card sets rotate out of Standard, however, in blocks. A given large expansion and its two small expansions—essentially a year of Magic expansions—enter Standard play as a new block when the large expansion rotates into the environment.
Example: The Invasion block rotated into the Standard environment when the Invasion set became legal for play. The Planeshift and Apocalypse sets are Invasion block expansions and are legal in Standard. The Invasion, Planeshift, and Apocalypse sets will rotate out of Standard together when the next large expansion after Odyssey (Onslaught) enters play on November 1, 2002 (two years after the Invasion set was introduced to the environment).
There are no cards currently banned in Standard.
Unless the DCI has made another announcement elsewhere, the Odyssey block rotates out 2 years after it is introduced into the environment... Though I wouldn't be surprised if they cut it short... I jus thope they leave it in for the miniscule 10 days... 
