Request for hacks: Project month notations

[Simon Thum <simon.thum@gmx.de>]

Hi all,

I'm working on a project where project dates were initially defined by a 
relative time given in months to some fixed date (the kick-off).

So I've got a lot of dates which look like "M19" (month 19 after 
kick-off), and I would like to use this notation (or something 
resembling it) for deadlines and other dates.

The most viable option in my view is to define an elisp function and use 
it as a sexp date. I guess I'll be able to figure out how to, but I 
thought maybe somebody else has a better idea.

One drawback is that I'd have (?) to define it in/through init.el, not 
in the project's org-mode file, which is unfortunate as the kick-off 
date is project-specific.

Ideas anyone?

Thanks in advance,

Simon