the event is future to the time of speaking.  In the other cases the event is regarded as present, i.e. you are reporting something which is happening or has just happened.  For something which happened in the past, you would use past perfect (this was the first time he had been to England).  This idiosyncrasy is regular with expressions like this is the first time.  With other expressions (this is the last time, for instance), the tenses would be different: this is the last time I come here - i.e. I will not come again.