How to override or stop circadian?

[infinitebuffalo]

I set up and initialized Circadian as suggested, but then decided I wanted for the moment to use a different theme. However, circadian doesn't allow the theme to be reset -- it's not that attempting to set the theme fails exactly, but after load-theme completes, circadian changes it back.

I don't even seem to be able to figure out how to turn off circadian so I can set a different theme, temporarily or permanently. Even uninstalling the package doesn't seem to kill it--or allow me to change themes....

So,

1. How does one override or pause circadian so you can change to a different theme temporarily?
2. How does one stop or disable circadian? Once started, does it just run without end until emacs itself is terminated or restarted?