When a latch catches on a door locking, the door "clacks" shut like the tongue clacks the roof of the mouth, the mouth roof.
When a train halts against a train car, the locks "clang," like the tongue settles against the roof of the mouth.
Noting the number of the day with a single digit when less than ten, and two digits only when ten or greater, followed by the number of the month likewise, and the number of the year always as a single digit, is a compact way to represent the date. The fact that the year is usually well-known makes the year unambiguous. But the day and month are ambiguous in cases when either one is more than a single digit and the day's second digit or the month's first digit is one or two. Although these cases do not occur the majority of the time they nevertheless occur often enough during the year to necessitate a distinguishing element to divide the day from the month. If this distinguishing element is graphical the date is representable in four digits for nine months of the year and in five digits for only three months. For its brevity, this system is very elegant; for its ambimorphity, it is spectacular.
The fact that four digits represent the day of the year for three quarters of the year bears the characteristic that the notation of most days progressively resembles the common notation of a single year from the days numbered ten to the days numbered twenty.