EST generally means Eastern Standard, most likely due to the fact that its the first timezone here i the states/it's New York's timezone (rather, who it's used for so much stuff here in the states)
Yes - our country has an East too.. we sometimes even have standards.. also clocks!
EST is Eastern Standard Time here too.
Our largest city Sydney uses it - and also our capital city Canberra plus Melbourne, Brisbane and other population centres.
Being the 'east' it's the first timezone here too (how about that!)
It's also used for 'so much stuff' here.
So.. the upshot is - You don't want to hear times quoted in our EST - we don't want to hear times in your EST.
These sorts of abbreviations are parochial and ambiguous in a forum like this.
UTC is a global reference point.