Due to multiple requests, I wrote an axe clock library, LIBCLOCK. See CLOCKTST for example code.

Axe Code Function on calculators with a clock (function on calculators without a clock).

Main functions:
ClkOf() Turns the clock off (does nothing).
ClkOn() Turns the clock on (does nothing).
IsClk() Returns 1 if the clock is on, 0 if off (returns 0).
°A:GetDT() Gets the current date and time. Sets 6 consecutive variables, or 6 consecutive words, starting at the passed in address.  In this example, A = year, B = month, C = day, D = hour, E = minute, F = second (returns midnight of January 1, 1997). Do not pass in °r₁.
SetDT(year,month,day,hour,minute,second) Sets the current date and time (does nothing relatively slowly).
DOfWk(year,month,day) Returns the day of the week of the specified date, 1 = Sunday, ..., 7 = Saturday.

Low level functions:
°A:GetRT() Gets the current raw time. Sets 2 consecutive variables, or 2 consecutive words, starting at the passed in address.  In this example, AB = seconds since January 1, 1997 (AB = 0).
°A:SetRT() Sets the current raw time.  Uses 2 consecutive variables, or 2 consecutive words, starting at the passed in address (does nothing).

Bonus functions:
Mul21(r₁,r₂,r₃) Multiplies r₁r₂ by r₃ and stores the result in r₁r₂.
Div21(r₁,r₂,r₃) Divides r₁r₂ by r₃ and stores the result in r₁r₂, and the remainder in r₄. Edit: I think r₃ must be < 256.