Appropriately, at the time of year when Bank Holidays are thick on the ground in the UK, I've been doing some freelance work on an international business resources website. Updating their political, economic notes and public holiday dates for 27 countries.
The biggest headache is checking dates for up-coming public holidays. You'd think that most of these would be pretty easy, eg. 'Victory Day' falls on 1st Aug every year... but it doesn't necessarily!
The world's countries seem pretty evenly split between regimes where, if the 1st Aug falls on the weekend, tough! No forwarding to Monday nor any days off in lieu! And the more relaxed governments who automatically move every holiday forward or back if there's any kind of date clash.
Then there are the festivals whose dates are set by a lunar calendar, or religious calendar... anything but the Gregorian Calendar. This means that some festivals can leap about all over the place from year to year, and in some cases, such as the Hari Raya Haji (Feast of the Sacrifice), appear twice in one year and then skip the next year!
And if that isn't enough to wrong-foot you, nothing, it turns out, is fixed forever. Governments add holidays (Japan has introduced a controversial Emperor Day into their calendar which in turn has bumped another holiday to another date) and take away national holidays (In 2005 Russia dropped the old Nov 7 Revolution Day that marked the Communist revolution, and Boris Yeltsin's Dec 12 Constitution Day holiday introduced by President Boris Yeltsin in 1993 to celebrate the adoption of Russia's current constitution. To make up for the loss they added some days this year to the New Year holiday extending it into the Russian Orthodox Christmas in Jan to make it one long holiday) or switch them from one calendar to another (South Korea is moving some of its festivals and holidays from their solar/lunar calendar to a Western Gregorian calendar).
Blimey! Who'd be a diary publisher!!
And even then, no two lists of a country's National Holidays agree. Take any list of a country's public holidays and I can show you another seemingly authoritative list of its holidays that will have additional holidays (or fewer) and at least one different date.
But this is the bit that really surprised me.
Given how incredibly complicated and inconsistent it is, you'd think for everybody's benefit - authorities, businesses, citizens - that it would be important to calculate and publish official lists of all these dates way in advance so everybody can forward plan.
But hardly anybody does. It is almost impossible to find a list of public holiday dates beyond the middle of next year (2007). In some cases they are not that far advanced at all - the Swedish Tourist Board is currently listing public hols in 2005.
If ever there was a case for centralisation... Perhaps the United Nations website should host a definitive version of the world's public holidays.