If you are getting a message popping up on certain web sites when using IE that says The security certificate has expired or is not yet valid, you will want to check the date and time your computer is set to. An incorrect date or time is the most common cause for this error.
Just double-click on the time in the lower right corner on the Taskbar, select “Change date and time settings” > “Change date and time…“, then set the time correctly. Be sure to check the time, month, date and the year. As soon as it is corrected, this will usually fix this issue.
If the time keeps switching on your computer, it may need a new CMOS battery. You can usually replace them yourself. They usually are the same type of battery as you would use in a watch.