Then upon a day king Anguish asked Sir Tristram why he asked not his boon, for whatsoever he had promised him he should have it without fail.
Then upon a day Bellangere the constable came to Anglides and said, Madam, it were time that my lord Alisander were made knight, for he is a passing strong young man.
Then upon a day this lord of that castle, Sir Bliant, took his arms on horseback with a spear to seek adventures.
Then upon B or C arising, the high contracting parties, though desperately and equally pacific, find themselves committed to war actually by a treaty of lasting peace.
The above list will hopefully provide you with a few useful examples demonstrating the appropriate usage of "then upon" in a variety of sentences. We hope that you will now be able to make sentences using this group of words.