Easy Timer/Countdown/Chronometer Library – easytimer.js
easytimer.js is an easy-to-use JavaScript library that allows to count up to or countdown from a given value with callback support.
JavaScript & CSS timer
Feature-rich Countdown/Clock/Timer In Vanilla JavaScript – W3FClockTimer
W3FClockTimer is a feature-rich JavaScript to create countdown, clock, timer components on the app.
Lightweight JavaScript Timer Library – Timer.js
Timer.js is a lightweight, generic JavaScript timer library which allows you to start / stop / resume / reset a timer inside any HTML element.
Minimalist Countdown Timer with timerJS.js
timerJS.js is a super tiny javascript counter library that counts down in in seconds, minutes, hours and days to any date/time.