A simple solution to monthly databases 
that's working fine for me at Nuestro Calendario  

Step 1 

Start by finding this part of the code by Selena near the top: 

    # Now rename some other variables with the same idea...  

    if ($form_data{'year'} ne "") 
    { 
    $current_year = "$form_data{'year'}"; 
    } 
    else 
    { 
    $current_year = "$the_current_year"; 
    }  

Step 2 

Then add these two Chuck Mayo  modifications (originally for another routine)  
to this next part of Selena's code: 

    if ($form_data{'month'} eq "") 
    { 
    @mymonth = &make_month_array(&today); 
    $current_month_name = &monthname($currentmonth); 
    $cal_month = $currentmonth; # <---Chuck Mayo modification
    } 
    else 
    { 
    @mymonth = &make_month_array(&jday($form_data{'month'},1,$current_year)); 
    $current_month_name = &monthname($form_data{'month'}); 
    $cal_month = $form_data{'month'}; # <---Chuck Mayo modification
    } 

Now we can use  $cal_month to separate the events databases by months.  
$cal_month  corresponds to the number of each month 1, 2, 3 and so on. 

Step 3

Create individual events files with this format:

    calendar.events.1 
    calendar.events.2
    calendar.events.3 

...and so on for the twelve months with the same permissions 
and location as the original calendar.events file. 

note: I took my old calendar.events file, sorted it in a spreadsheet and then 
divided the events into the 12 files.

Step 4

Now find all occurences of

    $database_file or "$database_file"

and rename them all: 

    "$database_file.$cal_month" 

note:In Selenas code (Version: 4.0) some of these ocurrences have quotes 
and others do not. Make sure they ALL have the quotes. 

That's all!

-----------------------

From : Daniel McFall <dmcfall@indcomputer.com>

On the Cool Hacks page, there is a code modification to divide the
calendar.events file into twelve separate files depending on the number
of the month.  It says to replace every instance of $database_file or
"$database_file" with "$database_file.$cal_month".  This is not
correct.  There are several instances when $database_file is used in an
error message.  These instances should simply be replaced by
$database_file.$cal_month to prevent closing the double quotes of the
error message too early.