The code to display a b-day message would look like this:

In file arch/arm/special/notify.c:
In function init_notify():
Code:
void
init_notify (void)
{
        const char *msg = NULL;
        tm_t tm;

        hijack_convert_time(CURRENT_TIME + hijack_time_offset, &tm);
        if (hjcd(&tm,0,12,24,25))
                msg = "Happy Birthday, Jack!;
        if (msg)
                show_message(msg, 10*HZ);
}

The hjcd() function wants timestamp, year, month, startday, endday as parameters. Take it from there.

-ml