The standard US date format is MM/DD/YYYY. The standard East Asian date format (China, Japan, Korea) is YYYY/MM/DD. Most everywhere else (Britain, Europe, India, Australia, etc) uses DD/MM/YYYY. All of these could be properly marketed as "date serial numbers" to the right audience.
Unfortunately for you, nobody uses YYYY/DD/MM as a standard date format. Though if somebody wrote "1999/16/05" you would probably be able to figure out it's a date, and which specific date they're trying to refer to (since there aren't sixteen months in a year), calling this note a "date serial number" would be a stretch. And because of that stretch, I can't see anyone paying a premium for it - not even tornado watchers from Iowa.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis