It's age 21, but it's not legal yet.
It will only become legal when the governor formally signs the amendment into law, which could be as late as Jan. 5. County clerks have until the end of today to send in vote tallies, and the Sec. of State has until Dec. 6 to certify. Then the governor has up to 30 days to sign.
Or so my handy Google search of the Internet tells me.