If you have successfully installed Visual Studio 2012 express and obtained the license for windows store app development but totally unable to install the Windows Phone 8 SDK with the same error messages as given in below figure then you should try the most common tips which is described below.
- Windows Software Development Kit Tools for Windows Store.A required certificate is not valid within its validity period when verifying against the current system clock or timestamp in the signed file.
- Windows Phone SDK 8.0 Assemblies User Cancellation installation
- Windows Phone 8.0 Emulation Images A required certificate is not within its validity period when verifying aginst the current system clock or the timestamp in the signed file.
Possible Reason :
Your setup might be expired. There is quite chances that you are getting error just because of your WP8 SDK setup is expired. This error might look some weird but this is the true. I've seen many user faced same problem and then successfully installed their setup just by using a simple trick.
How to Solve :
changed the system date as per mentioned in Digital Signature of WPexpress.exe inside WP8 SDK
When you start installation, you can see the certification of application. It shall show the date valid from xxx to xxx. To solve this issue go to your setup file of Windows phone 8 SDK and right click on right click on WPexpress_full.exe and go to properties and then click on Digital Signatures tab check the time stamp and change your system's time within the period mentioned in the timestamp tab.
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