Hidden features in digital alarm clock radios

When I was younger — I’m not sure how young, though I’m certain it was before high school — I was intrigued by my digital alarm clock radio. It was the kind where pressing the “Sleep” button turned on the radio and displayed 0:59 as long as you held the button. It would play for 59 minutes, then shut off automatically.

Back then, I discovered the following features:

• If I held “Sleep” down, then pressed the “Hour” button, it changed to 1:59. If I pressed “Minute”, it would decrement the minutes. Thus, it was possible to set it to play for, say, ten minutes, then shut off.
• Holding down “Alarm” and pressing “Sleep” button would display the last digit of the minutes and the seconds. Holding “Minute” would cause the seconds to stop. Each press of “Hour” would reset the seconds to zero, and if the seconds were 30 or greater, it would increment the minutes. Thus, it was possible to set the clock exactly and resynchronize it when necessary.
• Pressing both “Hour” and “Minute” while holding down “Alarm” reset the alarm time to midnight.

The software in these clocks must be available on a standard chip somewhere, because the clock in Elena’s room and the Dora the Explorer clock in Katrina’s room have the same features.

UPDATE: There is a common chip! Actually, several manufacturers make chips with these features. The NTE NTE2062 [35k PDF], the Sanyo LM8560B [789k PDF], the UTC LM8560 [92k PDF], and the TI TMS3450NL have these features listed on their data sheets.