2190s

Timeline
Decades:	2160s - 2170s - 2180s - 2190s - 2200s - 2210s - 2220s (stardates {{{stardates}}})
Centuries:	21st century - 22nd century - 23rd century

Years[]

Rigel XII is settled by Human and Andorian prospectors, who establish a few scattered mining colonies.^[1]

↑ Decipher RPG module: Worlds
↑ TOS novel: Burning Dreams puts Christopher Pike's birth in 2219, and mentions Vina was thirteen years his senior, hence a birth year for Vina of 2206. Theo was said to be "more than a decade" older than Vina, so the question is "How much more?" Given that he's also described as "boyish" and a "young professor", and that some other phrase (implying a longer time) wasn't used to describe his age, the most likely answer is "Not much." If Theo was around 11-15 years older than Vina, then his birth would have been sometime between 2191 and 2195 (with an outside chance of something earlier). Hence, "circa the early 2190s".