Here's the latest scoop from Jon D., a member of the campaign management team, about a much requested feature coming soon to all AdWords accounts:

Currently, all AdWords accounts are set to Pacific Time. However, in the coming weeks you’ll see a message in your account inviting you to set your account's local time zone. This means your entire account, including all ad serving, reporting, and billing, will be calculated and managed according to the time zone of your choice.

It’s important to note that your account time zone can be set only once, so please choose wisely! Also, if you don't select a different time zone, your account will remain on Pacific Time.