If you want to be the first one to wish someone on their birthday. This website is the perfect solution for you.
Letter Me later .com allows you to schedule the email to be sent later.
You need to create a free account to be able to use this feature. Once you create the account, you will be able to link the existing email account with the Letter Me later. During the registration process care should be taken to see the timezone set. Because depending upon the time zone you set, email will be scheduled to be sent later!
One more interesting feature is that, email will be sent to the receipient , from the linked email id, not from the website. So, you may need to enable the POP3 service with the email account linked.