In general, you can not infer anything about model training and date cutoffs (or other model metadata) from the output because it might just be a statistically probable hallucination based on the training dataset.
The only way to really know any model metadata like training cutoff dates is to have someone at OpenAI actually vouch for it because they're the only ones that really know what data sets were used to train the model and whatever is the latest item included in it.