To use this script, simply replace whatever variable you want in
current_date="$Y/$m/$d/"
with whatever you want to add to your web page.
Next, change the lines you want to edit (#a=append, #i=insert, #d=delete, etc. Run man ed to learn more) in the script.
Finally, setup a crontab job for when you want the page updated. Such as:
0 0 1-31 1-12 * (SCRIPT LOCATION/SCRIPT)

The time and date fields are:

field allowed values
----- --------------
hour 0-23
day of month 1-31
month 1-12 (or names, see below)
day of week 0-7 (0 or 7 is Sun, or use names)

Where x x x x x x = Minute(0-59) Hour(0-23) Day(1-31) Month (1-12, or names) Day of Week(1-7,name of days) location of the script(such as /tmp/junk.sh)

And you now have a script that will change the date. The above example changes the date every day of the month, at midnight, every month of the year. It comes in useful as you can see below:
The current date is:
February 24, 2003
See how easy it is?
Didn't even have to use CGI/PERL, XML, PHP, or another compromisable scripting format....