Instead of asking "When did Yahoo buy Flickr?", think that a page that contains a statement that starts with "Yahoo bought Flickr in" should answer your question.
Step 1 - use quotes
Search for "Yahoo bought Flickr in" and you'll actually get the answer in the snippets. Not all the statements will give the same answer, so try to find the most popular opinion or the most reputable source.
That's great, but what if you want to find more complex information, like Yahoo's acquisitions from 2005 and their dates? The template for statements should be "Yahoo bought [company name] in [month] 2005". Replace the words in brackets with an wildcard.
Step 2 - use wildcards
Search for "Yahoo bought * in * 2005". A wildcard replaces one or more keywords, but you'll get pretty accurate data, like "Yahoo bought Konfabulator in July 2005" or "Yahoo bought the social bookmarking site Delicious in December 2005").
But how do you know that your template is good enough? To improve the performance, let Google match the synonyms of important keywords. Use OR between the synonyms of a word.
Step 3 - use OR
Search for "Yahoo bought OR acquired * in * 2005". You'll get the results for these two queries combined: "Yahoo bought * in * 2005" and "Yahoo acquired * in * 2005".
If you want to find some Yahoo acquisitions over the years, try the special syntax for intervals. To match all the integers between 1997 and 2007, add this to a query 1997..2007. This also works with currencies and measurement units.
Step 4 - use intervals
Search for "Yahoo bought OR acquired * in * 1997..2007". Although Yahoo was launched in 1994, they started to acquire other companies in 1997, after the IPO.
Of course, you'll say that a Wikipedia article about Yahoo contains all these acquisitions, but this was just an example. It works with almost any kinds of facts, as long as you use good templates and it has the major advantage that you'll see the answers in the snippets and you don't have to visit each search result. I found this extremely useful on a mobile phone, where it's difficult to read web pages and to find something inside them.
