CBS' new series "Supergirl," starring Melissa Benoit in the titular role, is set to premiere this fall, but one of the things that has confused many fans ever since the trailer came out is the age difference between Supergirl and Superman. A newly released timeline finally answers this issue. 

In the trailer, Kal-El aka Superman and his cousin Kara Zor-El aka Supergirl are sent to Earth at the same time so they can escape Krypton's destruction. At this point, Kal-El is an infant while Kara is thirteen years old. 

However, the trailer later reveals that Kal-El has been Superman on Earth for years before Kara decides to don a cape of her own, indicating that Kal-El is now older than Kara. According to a report from Screen Rant, this is possible because of the Phantom Zone.

According to the timeline, Krypton explodes in 1982. Infant Kal-El and thirteen year old Kara escape the planet. Kal-El arrives on Earth in the same year, with no issues. Kara's shuttle is knocked off course and enters the Phantom Zone, alongside Port Razz, and this locks her in time. 

In 2006, something causes the Phantom Zone to open, allowing Kara to continue on to Earth. Port Razz also heads to Earth, allowing the Kryptonian prisoners inside to escape. They leave their prison and go into hiding. 

At this point Kara is still thirteen but Kal-El has aged to 24 years. As Superman, he takes the young Kara to scientists Fred and Sylvia Danvers who adopt Kara as their own. 

In 2014, the Port Razz prisoners come out of hiding and begin their assault on Earth.

By 2015, Superman, now 33 years old, is busy saving Metropolis. Kara, now 22, lives in National City where she begins her career as Supergirl. 

The timeline also confirms that the television series is separate from the DC cinematic universe although it is still open to crossing over with "Arrow" and "The Flash" as they are produced by the same team, albeit on different networks.