How to find out what year house was built?

Currently filling in details to get a QS report.

My question is, is there anywhere online where I can find out when construction was started on the property or is the council the best place to start?

I rang the council and to my surprise once I got put through to the correct dept
had an answer within 1 min. I was all geared up for a game of council "phone tag".
I would goto council and ask to see your file. They may have to pull it out of archives but that will tell you when the plans were approved anyway. If it is a new dwelling you can do a DA search on most councils websites.
The certificate of occupancy or plan of subdivision will help. Look in your contract of purchase or do a title search at your State's land titles office.
I rang up the council yesterday and got a response within 1 min... really was quite surprised too.

except, I forgot to ask about the age of the granny flat on the property, so I'll have to ring up again...