We will return in two of your Earth days.
I wish to purchase one of your Earth pizzas, fellow typical human who, like me, is totally not from any other planet.
Does the cliché “[number] of your Earth [noun]s” have a known origin? In which B-movie was it first uttered – or, failing that, which was most responsible for making it a cliché?
If you allow for fantastic fiction, units of money, and mortality rather than Earth nature, Charles Dickens's A Christmas Carol, published 19 December 1843 states that the Ghost of Christmas Past comments on Old Fezziwig:
"Why! Is it not? He has spent but a few pounds of your mortal money: three or four perhaps. Is that so much that he deserves this praise?"
For a more sci-fi perspective, and calling out Earth non-explicitly, Plan 9 From Outer Space (1959), Eros comments on Earth technology:
"Since the beginning of your time, we have been far beyond your planet. It has taken you centuries to even grasp what we developed eons of your years ago."
Less explicitly (and back to fantasy, or maybe eschatology), Isaac Asimov's The Last Trump, published June 1955, has Etherial ask about the scheduled date of the end of the world as follows in his (successful) argument that it's unenforceable due to how non-specific it is because of how many ways Earth does dates:
"The document, approved by the Council of Ascendants and signed by yourself, authorizes the Day of Resurrection at a specific time of a specific day of the year 1957 as Earthmen count time."
1929: "Venus Liberated", a novella by Harl Vincent in Amazing Stories Quarterly, Summer 1929, available at the Internet Archive. This issue is dated July 20,1929, on the contents page. The excerpt below is from page 302, column 2.
"However, I shall not trouble you for ten of your earth days. I shall give you my message now and allow you sufficient time to communicate it to your people and to find an answer to my pleadings. That there be no doubt in the minds of your people of the authenticity of my message, I shall arrange a demonstration on my world which your scientific men should be able to view through their optical instruments. We have endeavored to signal your world for ages but it has been evident to us that our signals were unseen. Even now we have no assurance that your optical instruments are sufficiently powerful to locate the prepared new signal. But we have hopes that they are and our signal will be of such magnitude that even with the poorest kind of instruments it should be observed. This signal is solely for the purpose of convincing your world that the thoughts you are now receiving do actually come from my planet.
"I am Thalia, queen of the planet Venus, in your own solar system. This may seem absurd to you and to your people. They may disbelieve your word when it is given forth. But they can not disbelieve my signal. I shall now set the date and the time for this sign. During the fifth darkness from this, at one-half revolution of your earth after the sun crosses the meridian at which my thought waves are directed, we shall project into the heavens a beam of ultra-violet light. [. . .]
