I'm one of those people who actually uses the international information pages in my planner. Several brands of planners have good international information including dialing codes, time zones and country holidays. I have found that the international information included in the Filofax diary inserts is some of the best and most comprehensive in the planner world.
The international information pages included in the standard Filofax monthly or weekly diary inserts are:
Notable Dates for the year for the USA, Canada, UK, Ireland and Australia.
Religious Festivals and holidays for the following religions: Christian-Western, Christian-Eastern Orthodox, Islamic, Hindu, Buddhist, Sikh, Jewish and Chinese. I especially appreciate this list as I'm about to move to a country where Christian, Islamic, Hindu, Chinese, Buddhist and probably others are recognized.
European Union Members for the current year are listed with their capital city, currency, time zone, dialing codes to AND from (which are hard to find in most planners) and dates of their national holidays.
International Information has this same info listed for many countries of the world, including Indonesia much to my delight!
Weights and Measures is a page I use often, especially the Temperature Conversion scale.
The World and Time has loads of interesting facts about seasons, days, years and more.
World Temperature Guide has average daily temperatures for many cities around the world. Here's an interesting fact: I'm about to move to Jakarta, which is on the list. If you average the listed temperatures given for the year, Jakarta shares the highest annual average temperature with Bangkok (28.33 degrees C). Guess which city has the coldest average annual temperature? Moscow, where I used to live, at 5 degrees C. One extreme to the other!
Clothing Size Equivalents has men's, women's and children's clothing and shoe sizes in American, British and European sizes. I refer to this page a fair amount, and I especially appreciate they included children's sizes which planners rarely do.
Something else I really appreciate is that Filofax prints holidays on the day spaces in the weekly diary pages. It's that much less work for me because if they're not pre-printed, I hand-write in holidays. (Click on the photos for a larger view.)
Thank you Filofax!