What time zone does ET stand for?

I've been looking for it for days and I answered a question on a Mod's profile and I realized that EDT stands for Eastern Daylight Time while EST stands for Eastern Standard Time. In another part of the world, I heard Australia for example could be using ET but then I associated the ET for meaning European Time. I'm so confused and curious. And also, when the red warning sign says "Due to maintenance, Yahoo! Answers will not be available on Monday starting at 2am ET. For more information, read our blog." are they referring to a time zone from the United States or some other country in the world?