Solution of "Expired Certificate" error

When I try to install a sofware or application in my phone then this message shown ''Expired Certificate''. What is the solution?

If you face "Expired Certificate" problem, please set your phone date to 2007/01/01 or
2007/05/05 or 2006/01/01 before you install the
program or game.
You can set the correct date back after the program or theme is installed.

If your phone won't let you install applications still, then go to your phone's
"Application Manager"
menu,
Press "Options",
Press "Settings",
Make sure "Software installation" is set to "All",
And "Online Certificate Check" is set to "Off".