The software giant announced in November that the change would take place in the first quarter of 2013. Originally called MSN Messenger, Windows Live Messenger will start to be closed down on 8 April.
The Skype blog said: "The upgrade from Messenger to Skype on Windows desktop will start on April 8. The process will take a few weeks to complete. We'll start the upgrades with our English language clients, and finish up with Brazilian Portuguese on April 30 or later."
There is only one exception which is China where Messenger will continue to be available. Skype is available across Windows, Mac, iOS, Windows Phone, Android and will be coming to BlackBerry 10 soon.
To make the transition as smooth as possible, users will be able to sign into Skype with their Windows Live Messenger log in details. Skype serves 280 million users per month, according to the firm.
Skype has also announced a new feature for iOS, Android and Mac users in which they can record and send a video voicemail message. Users will be able to pre-record and send a video clip up to three minutes long for free. Bizarrely, there's no word on when this feature will reach Windows users even though Skype is owned by Microsoft.
"We want everyone who uses Messenger to have a positive experience. Upgrading to Skype can help you communicate in flexible ways, and be connected on more devices and platforms," said Skype.