Microsoft’s Windows Phone 7.5 operating system will launch on September 1, according to reports.

Commonly referred to as Windows Phone Mango, its codename, Windows Phone 7.5 was finalized by the software giant in late July. UK site Pocket-Lint claims, through “trusted sources”, that Microsoft is planning to launch the Windows Phone 7.5 update on September 1. “The date we now understand to be chosen is important because it ties in with IFA, Europe’s largest consumer electronics show in Berlin, and means that companies like Samsung, Acer, ZTE and LG will be able to show off new devices with Mango installed,” said Pocket-Lint on Thursday.

WinRumors understands that Microsoft will announce several Windows Phone 7.5 devices on September 1 but that the update for existing devices will not be made available immediately. Microsoft is understood to be preparing a rolling update instead of a single “big bang” approach. Windows Phone developers will be able to submit 7.5 applications on August 22 and the software maker will release the Windows Phone Mango RC development tools on that day too. Microsoft will likely wait until its development tools are fully baked and OEMs/carriers sign off on Mango before pushing the update to existing devices.

Microsoft’s Nokia partnership will likely be strengthened by the launch of its first Windows Phone 7.5 device in October. Nokia is understood to be planning a launch party event for its Windows Phone device at Nokia World on October 26. The majority of new Windows Phone 7.5 devices will be made available in time for the important holiday season.