question on the 'calendar' function

[o1bigtenor]

Greetings

I am in the process of learning my first computer programming language
(unless g-code counts and then it is my second - - - grin). It
definitely is a big world out there.

The calendar function has a lot of versatility and shows care in its
development.

There is one area where I don't understand if I even could use this
function or if I need to look to something(s) else to achieve what I
need.

For planning I need to be able to easily look backward 6 months and
forward at least 12 and better 18 months and would prefer perhaps even
a total of 36 (and even 60 might be useful) months of calendar
available. It could be useful to see the longer time spans as weeks
rather than as days but seeing the larger time frames only as months
would enable the planning that I need to do.

Do I need to (somehow and I have no idea how) extend the calendar function?
Is there some other way of displaying dates/calendars that would allow
me to achieve my needed span?

TIA