This Monday, Microsoft adCenter will begin to power the search ads on Yahoo Search and partners. October 11th is the day Yahoo announced as the big transition of ad serving.
The transition will begin Monday and take about two weeks to roll out completely. Again, this is only impacting U.S. and Canadian searchers. Yahoo said:
While many advertisers have initiated their account transitions to adCenter, the other big step to this process is the transition of Yahoo! ad serving to adCenter. We expect this to happen gradually over a two-week period, beginning as early as October 11. In advance of this transition, we plan to increase the percentage of traffic involved in the adCenter ad serving test, which we believe will help ensure a smooth transition.
So if you have not yet transitioned your Yahoo account to Microsoft adCenter, you have a few more days.