- Dating is conjecture, based on the statement that Yabapmat served as Gelta's capital "for thirty-eight generations", and assuming a generation of twenty years.
By the 23rd century, Gelta had become the dominant sociopolitical entity on Mestiko, as well as the most scientifically advanced. With the support of other nations, such as Larenda, Gelta scientists were responsible for the development of Mestiko's first warp vessel. This, as well as Gelta's leadership in the global Zamestaad and stated goal to use warp technology to the benefit of all Mestiko, led to Federation sociologists making a covert first contact with Gelta officials.
When a rogue pulsar passed through the Mestiko system in 2265, Gelta was directly exposed to the full force of the radiation to hit the planet, and as a result suffered the most immediate and catastrophic damage caused by "the Pulse". (TOS eBook: Mere Anarchy: Things Fall Apart)
Gelta apparently ceased to exist as a political entity in the wake of the Pulse; by 2293, it was referred to as "Gelta province." That same year, its famed hotsprings were again accepting visitors. (TOS eBook: Mere Anarchy: Its Hour Come Round)