Scheduling e-mails in web based mail services

In web based e-mail services like yahoo mail & gmail, I always feel 1 feature is missing. That is setting timer to send mails. Suppose, if tomorrow is my friend’s birthday, I will write an email and set a timer to deliver the email at night 12′ clock. I don’t have to be awake till 12′ clock to wish him.

In the view part, only change is “Drop down” should be provided at the send button to select the time.

I know we can achieve this using schedulers present in our machines. But, feature like this in web based mail services will reach more audience. If this option is provided in yahoo or gmail, that will be very nice.