> I'm interested in trying this, can you give me more detailed  
> information about how to approach the problem?

There are several parts

Timebase
Timekeeping
Alarms
Interface

Timebase is the "tick" of your calendar. This can be from an
external source, such as mains cycles, oscillator or IC. The
gif I posted shows a 0.5Hz output but an alternating 0.5Hz
is available at the other output pin -> 1Hz if you use both.
If you want a less fine resolution, you can divide this down
with 4040(s) to get 1 pulse per minute or hour or day

Timekeeping is what you do with the tick. You need registers
for ticks/seconds, minutes, hours, days, months, and years.
A table for days per month will be needed, and leap year
testing is going to be straightforward for quite a while

Every tick that comes in will increment the lowest register, be
it seconds or minutes etc. At this time you perform rollover
tests to see if the tick increment will ripple up through the
higher registers. You also compare the registers to the alarm(s).
A separate register to say whether alarms are enabled and if
so, will make that test more efficient. You do what you need
to if there's a time-alarm match. Maybe cancel the alarm or
keep it enabled for the next hour or day

Alarms will have the same registers as timekeeping. A separate
register or flag for each could tell the PIC what to do at that
alarm, eg '0' turn an I/O off, '1' turn it on etc

Interface is how you set the time/alarms and display and
I/O driving. To make things easy you'll need possibly an LCD
and a few buttons. This could be detachable and used only
for setting registers. The simplest solution for navigating through
a menu system, selecting items and changing them IMHO would
most probably be a mouse wheel and an Enter button

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