UPDATE 1 PM: The Daily Show‘s monthly average only includes original telecasts as is the practice in cable. Meanwhile, the averages for the broadcast late night shows include all telecasts, original and repeats. Both Letterman and Leno had one dark week in October. Still pretty impressive result for The Daily Show but it is fair to compare apples to apples.

PREVIOUS: This is a major achievement for Comedy Central’s The Daily Show with Jon Stewart and possibly an indication of a sea change in latenight that has been brewing for awhile as younger viewers have been gradually migrating from broadcast to cable. Traditionally dominant among young men and adults 18-34, The Daily Show with Jon Stewart finished the month of October as the No. late night talk show in the big boys’ demo of Adults 18-49. This is the first time that any late night talk show other than The Tonight Show or Late Night with David Letterman has claimed the top spot in the key demographic. Of course, Daily Show‘s October numbers got a boost from the show’s coverage tied to the Rally to Restore Sanity and/or Fear last weekend and all the publicity surrounding the event. But with broadcast latenight shows’ audiences aging along with their hosts, they have been consistently losing ground to hipper upstarts such as Comedy Central’s The Daily Show and The Colbert Report. Things will get even more interesting next week when Conan O’Brien enters the fray on TBS. The bar for him is not very high as the show he will replace in the 11 PM hour on TBS, Lopez Tonight, is currently the lowest-rated latenight show on any network. Here are all entertainment late night shows’ 18-49 rankings for October:

1. The Daily Show with Jon Stewart – 1.3 million viewers in 18-49

2. The Tonight Show with Jay Leno – 1.2 million viewers

3. Late Show with David Letterman – 1.2 million viewers

4. The Colbert Report – 900,000 viewers

5. Late Night with Jimmy Fallon – 800,000 viewers

6. The Late Late Show with Craig Ferguson – 700,000

7. Jimmy Kimmel Live – 700,000

8. Chelsea Lately – 650,000

9. Lopez Tonight” – 450,000