Microsoft is planning to release its Windows Phone 8.1 update to developers in April. While the software maker unveiled a number of new features in the update during its Build conference this week, no official date was provided. Neowin has published a Windows Phone engineering email which reveals Microsoft is aiming to release the Windows Phone 8.1 developer preview on April 14th. The Verge can confirm this date is accurate, and Microsoft is currently aiming to distribute Windows Phone 8.1 to developers on April 14th. Microsoft is tweaking the final version of Windows Phone 8.1, and sources familiar with the company’s plans tell The Verge this date could slip, but it’s the current plan. Microsoft’s developer preview program for Windows Phone allows handset owners to bypass carriers and get the latest updates.