Small userscript to show a new YouTube time elapsed/duration when the playback speed is changed.
The best way to use this script is with some sort of script injector. I use Enhancer for YouTube, where you can paste in the script.js file contents and tick the "Automatically execute the script" checkbox.
This script may work in Greasemonkey and others but is untested in these.
Feel free to open any issues or PRs, I'll take a look at them if I get the time.