On how many days of the year are there virtually no holidays (when people get a day off at work) in any country?

My expectation would be zero and I did a little research on the web, but found no conclusive answers. Many calendars include all sorts of special days (like Earth Day) but workers do not necessarily get a day off. So I’m really just looking for national, religious and/or other general holidays.

The question is a bit more complicated because some holidays depends on other calendar schemes, many based on lunar years.

So we could also ask the question like this:

In 2010 on which days does the majority of (employed) people in the world have to work? And how many of them are there? A useful condition might be to exclude (regional) holidays observed by less than a million people.

Another question would be:

Which are the most global holidays in 2010 (observed in most countries)?