A one-time XVG coin event USDT/XVG on Bittrex has completed 1158 days ago, occurring on 12-31-2017.
In general, this subset of occurrences is positively influencing the cost of cryptocurrency.
As there were alternate occurrences neighboring this one, it cannot be affirmed that only USDT/XVG on Bittrex has impacted the XVG price, as other occurrences could also have an impact.