We as Americans seem to love the Anglo-Saxon genitive. If you doubt me, just glance through the posts here and note every time someone mistakes the Anglo-Saxon genitive for the plural. (you know, the guys who say: "We're gonna nuke the hell out of those darn Afghani's" instead of "What beef do we have with the Afghanis?")
So April 15th, 2001 is easier for us to swallow than 15th of April, 2001.
Frankly, I prefer using Roman numerals to indicate the month, as in:
1-X-2001