Introducing Gmail Custom Time(TM)
Be on time. Every time.*
How do I use it?
Just click "Set custom time" from the Compose view. Any email you send to the past appears in the proper chronological order in your recipient's inbox. You can opt for it to show up read or unread by selecting the appropriate option.
For an April Fools joke, I have to give it a thumbs up. You should check out their testimonials!