How to get first and last date of the quarter?

Quarter can mean different things for different people. Have you tried anything?

Today is 2015-12-07.  For us the first date of the quarter would be 2015-10-01.

I tried this: 

select year(sysdate) || '-' || (quarter(sysdate)-1)*3+1 || '-' || '01' 

result: 2015-10-01

My way was succesful, I was wondering if there is a better way.

The last date of the quarter would be 2015-12-31.

I tried this:

select date(year(date(current_date - EXTRACT(DOQ FROM CURRENT_DATE) + 1) + 100) || '-' || month(date(current_date - EXTRACT(DOQ FROM CURRENT_DATE) + 1) + 100) || '-' || '01') - 1

Result 2015-12-31

Result is successful, but method is a bit convoluted.

SELECT ADD_MONTHS(TRUNC( current_date, 'Q'), 3)-1;