nitinmauryalko

This plugin includes the option to display a current date and time in your sidebar using the built-in widget.

Clock_Widget

jordancalder

This plugin adds a countdown timer to your webpage with the use of a shortcode.
In Settings > WP Countdown Timer, set the datetime you want to count down towards and save.
Use the shortcode [countdown] on any page to display the countdown timer.

WordPress Countdown Timer

Wordpress plugin to add a countdown timer to your website. Display a timer and countdown to any day, time, or event.

Clock_Widget vs WordPress Countdown Timer