Lucinda Shen, writing for Fortune:

In the weeks following its earnings report in April, Apple looked like it was in a tough spot. Shares of the tech giant fell 13.4% between late April and May 12, after Apple reported that sales had dropped for the first time in 13 years. Shares rebounded slightly, before Warren Buffett, the Oracle of Omaha, disclosed his company’s $1.2 billion stake in the company on May 16.

Since then, shares of Apple have soared 9%—finally breaching the $100 mark, its highest point in a month.

Could be Buffett revealing his investment had an effect on the stock price, could be he knew the exact time to strike. Or both. Either way, looks like he just made his own shareholders some good money:

$1.2 billion x 9% = $108 million

Not bad for a couple of days work.