After the capability was discovered a few weeks ago, Twitter has officially announced the ability to schedule tweets to go live at a specific time. It's also possible to save tweet drafts for later.
Scheduled tweets RSS
Twitter is reportedly rolling out one of the most requested features for Twitter users - scheduling tweets. The feature has been present on some third party clients and is a welcome addition.
Twitter is testing out a new feature on Twitter.com that will finally allow you to schedule your tweets, something that has long been possible using the company's own TweetDeck client.