Board Thread:General Discussion/@comment-33623316-20180324010440/@comment-1916997-20180411142756

Eskaver wrote: Or the LWM for HH is different from the LWM for SB.

Robin did indeed age 18 years, because Henry finished Highschool in 2019 and Robin did three years or (Highschool) track.

Just because it’s 2017 in HH doesn’t mean anything about SB. There is no indication that they are in an alternate LWM, so that is highly speculative. I think the writers just wanted Robin to be an adult, and didn't care that it didn't fit with the timeline.