outlook 98 add in's

Outlook stores a read-only text file called Outlook.txt in the \Program Files\Microsoft Office\Office folder, which it uses for the Add Holidays feature.

The Outlook.txt file lists holidays in the following format:

[Country] ###
Holiday description, yyyy/mm/dd
Holiday description, yyyy/mm/dd

In the above format, ### is the total number of holidays listed for a particular country. Note that there is a space between the closing bracket and the number as well as a carriage return at the end of the line. On each holiday line, there is a comma and space between the holiday description and the date, as well as a carriage return at the end of the line. For example:

[United States] 3
Independence Day, 1997/07/04
Thanksgiving Day, 1997/11/27
Christmas Day, 1997/12/25"

Here's the article:
(Type the Q number in the Search box at support.microsoft.com)
How to Customize Outlook Calendar Holidays

Q180985

Here's the source for a perpetual calendar that can be set up for various countries:

www.timeanddate.com/calendar/