Code reveals that scheduling feature could be coming soon to Gmail's Android app
The code, discovered by Android Police, includes the words "schedule send" multiple times. Apparently, the new feature will be accessed by tapping on the overflow menu found on the Compose screen. No doubt that clicking on the link will allow you to set the date and time when you want your email to arrive.
Speaking of schedules, there is no clue as to when the Android Gmail app will get this feature, which certainly will come in handy for many users. If you don't want to wait for Google to eventually update the Gmail app with this capability, you can install the Boomerang Mail app on your Android or iOS device (see image at right) by clicking on the appropriate link: (iOS|Android).