You can do this legit by just completing a race for seven days in a row, if you want a time stamp. If you want to earn this as quick as possible, you can do this by changing the times on your console. However, your achievement will not have a time stamp when unlocked. If you do not know how to do this, follow my instructions below.
1. Disconnect from Xbox Live by removing your Ethernet cable or wireless adapter from your xbox.
2. On the dashboard, go to My Xbox > System Settings > Console Settings > Clock > Date and Time.
3. Change the date one day forward
4. Load up Skydrift
5. Play a race, survivor races will be the quickest if you come in last and are the first eliminated.
6. After the match ends, press until you are back at the main menu, and go to your dashboard.
7. While still disconnected from Xbox Live, repeat step two and just go forward again to the next day.
8. Rinse and repeat for seven days
Note: Some people have claimed it takes eight days for them to unlock. So if it doesn't unlock on the seventh day, keep trying.