One month ago, Skype celebrated its fifth anniversary.

On Sunday, the software company hit another milestone: the billionth download of Skype software.

CEO Josh Silverman noted at the main blog:

"A few minutes ago, something pretty cool happened. Someone, somewhere in the world, downloaded the billionth copy of Skype.

"It took us three and a half years, from August 2003 to February 2007, to reach the 500 million download mark, and then just 19 months for another 500 million copies to be downloaded. That's a pretty dizzying feat for a five-year old-software company, and one that we're all very proud of."

Silverman said Skype isn't resting on its laurels:

"Our ambition to make Skype available on as many devices as possible...bringing people closer to their friends, loved ones and colleagues - anywhere in the world; at work, home or play; and on any device.

"Here's to the next billion."