Using Chrome? Using Twitter? You better start using TweetDeck for Chrome, you won’t regret it. The main difference between this client and the desktop one, is that you only need Chrome to use it, no third-party programs to use it. In the latest release they added an extra button to the Compose Window, a clock.
That clock is not there to tell you the time, is there to schedule your tweets the easiest way possible. Click it. Next, set the time and date for the tweet.}
After the time is set, just click on Set Time. Then, send it.
These schedule tweets will appear on a new bar on the right. That way, you’ll have control over you schedule and never miss what you tweet.