Countdown timers are useful when you want to encourage more of your visitors to take a certain action or take advantage of a limited-time offer. There are plenty of fancy countdown plugins available for WordPress. The WordPress Countdown Widget is a lightweight plugin that lets you display a simple countdown/up timer on your website.
Once you add the widget to your sidebar, you will be able to change widget title, event title, date, color, format and other settings. You can also choose which direction your timer should go (up or down). This plugin has a widget and shortcode. You can download the plugin for free.