Microsoft's support for Windows Phone 8 and Windows Phone 7.8 will end in the second half of 2014, according to the software maker.

Microsoft listed the sunset dates on its Web site recently, with WP8 support ending July 8, 2014, and WP7.8 support ending Sept. 9, 2014.

Both dates are 18 months after the support lifecycle starting date. The updates provide changes and improvements to the OS, including security, that are distributed by either the wireless operator or the phone manufacturer, Microsoft said.

This short support lifecycle seems at odds with Microsoft's aim to establish the Windows Phone 8 operating system in the enterprise,where CIOs and IT teams see stability and predictability of the mobile OS as essential.

The support lifecycle for Windows RT, which runs on tablets from various manufacturers, has not been detailed, although Microsoft said last fall that the policy "will be communicated as available." As of Monday, that policy remained in place for Windows RT on the Microsoft site.

Last November, Microsoft said its support of Surface RT tablets (also running Windows RT) would expire April 11, 2017. That time frame is less than half the usual 10 years of support that Microsoft gives its software products. For its Windows Phones, the time frame is less than one-fifth as long.

The 18 months for Windows Phone support seems short even for a pure paly consumer product. Most mobile carriers, phone makers and phone OS makers typically view the lifetime of a phone as two years. That is one reason why carriers sign customers to two-year contracts.

Even some new phone models are being updated within 12 months, as has happened with the Samsung Galaxy S III introduced in 2012, which will be updated to the new Galaxy S4 when it ships this April.