Board Thread:General Discussion/@comment-71.37.202.154-20140725182057/@comment-26397825-20160419004432

The flashback episode was only about 6 months before the start of the show, acording to Gray in the Cast Commentary. They also make mention of how amazing it is that Cinder's hair grew that quickly.

So if they were 17-18 in the falshbakc, they'd still be 17-18 now.