HP -01 Owner's Manual page 92

Operational Description 90
Date Register. Each day in the 200-year calendar is represented internally by a number:
Date Day Number
January 1, 1900 0
January 2, 1900 1
9 ®
December 31, 2099 73048
When you press @@, the HP-01 changesthe displayed date entry to the appropriate internal
day number. Everytime the time register rolls over at midnight, the internal day number
increments by one. When you press @ to view the current date, the HP-01 converts the day
number back to MM-DD-YY or DD-MM-YY formatfor the display.
Alarm Register. The alarm accepts any time in a 24-hour day. When you press .. the
displayed time is loaded into the alarm register and the alarm is automatically armed. When the
alarm register matches the time register, the alarm sounds and is automatically disarmed.