Old Establishments

America's oldest college, Harvard University was established in 1636.
This date takes on the Yamasa Soy Sauce makers by a mere 9 years.
William and Mary is a then-lifetime younger, coming in at 1693.

News reports cite several examples of restaurants and inns dating back to the 11th century. The Hoshi Inn in Komatsu dates to 718.
As for an organization outside Japan, the Worshipful Company of Bakers dates to 1155. The Medieval guild is something you may have read about in your World History textbook. Nice to know that they're still alive and well.

One thing to take in mind is that most of these oldest establishments are not, and have never been in their histories, conglomerates!
A prime example of the dangers of diversification is Kongo Gumi, a Japanese Temple Building firm that has been in continuous family operation since 578, just a century after Ancient Rome's fall. However, the latest generation of family leaders branched out to commercial real estate in the 1980's, and, well, bad idea. The company, debt-ridden, was absorbed in 2007. Read this Bloomberg article:http://www.businessweek.com/smallbiz/content/apr2007/sb20070416_589621.htm