To fix this expired certificate error first thing you have to do is to set the date on your mobile device to one or two year prior to the current date. Then install the required item and put the date back to the actual Current year. That's it.
First method is the genuine reason of this type of problem. But sometime this problem can be solved from this method. Come in to "Menu" and click on "Tools"
In "Tools" click on the "Setting"
Come in to the "Applications"
In "Applications" menu click on the "App. Manager"
Change the "Software Installation" to "All".
Similarly change the "Online Certificate Check" to Off".
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