Upon is seldom used to express time.
(3) Reference, equal to about, concerning, etc.
I think that one abstains from writing on the immortality of the soul.—Emerson.
He pronounced a very flattering opinion upon my brother's promise of excellence.—De Quincey.
On my life, you are eighteen, and not a day more.—Aldrich.
Upon my reputation and credit.—Shakespeare
(5) Idiomatic phrases: on fire, on board, on high, on the wing, on the alert, on a sudden, on view, on trial, etc.
Exercise.—Find sentences with three uses of on or upon.