WordPress Countdown plugin is an nice tool to create and insert countdown timers into your posts/pages and widgets.
Wp Clock Counter Plugin Super Lightweight, Fully Responsive and easy to install.
YITH WooCommerce Product Countdown allows you to put a digital counter in the product pages
Uji Countdown - HTML5 Customizable Countdown Timer
Display an animated countdown clock on your sidebar. Select from several clock designs, colors, sizes, pictures and animations. Responsive plugin, ser
The official #1 most intelligent, scarcity countdown timer plugin ever created for WordPress to expire posts AND pages on autopilot!
WordPress plugin to add a countdown timer to your website. Display a timer and countdown to any day, time, or event.