Google says that the Golden Gate Bridge is 85 years old which is partially true since work began on the Golden Gate Bridge in 1933 which was 85 years ago as of 2018.
But to me I would say that the Golden Gate Bridge is 81 years old as of 2018 since 1937 is when the Golden Gate bridge was completed and opened.
So you could say that the bridge is 81 years old or 85 years old whichever way you want to determine the age of the bridge.
Either way the Golden Gate bridge is nearing 100 years old within 19 years.