The phrase "ago when he observed" is not correct in written English.
It is not a standard construction and lacks clarity in meaning.
Example: "It was a long time ago when he observed the unusual behavior of the animals."
Alternatives: "some time back when he noticed" or "previously when he saw".
Galileo noted this nearly 400 years ago when he observed sunspots.
A British naturalist named Alfred Russel Wallace noted as much more than a century ago, when he observed that the flora and fauna found on Lombok are remarkably different from those of Bali.
-JOHN LUKACS, Five Days in London, May 1940 Search and Destroy IF SUPREME COURT Chief Justice John Marshall was right 180 years ago when he observed that "the power to tax involves the power to destroy," then the members of the federal Advisory Commission on Electronic Commerce should ask themselves today: Will taxing the Internet kill this revolutionary medium in the cradle?
The notion crystallized one day 18 years ago in the monkey-filled jungles of Panama, when he observed an abundance of rotting fruit littering the forest floor, fragrant with the smell of alcohol.
Dr. Hare first noticed something odd about them more than a decade ago when he observed a squirrel that looked as if it was vocalizing, but no sound came out.
Cardinal Zen's remarks represented a shift in his stance compared with two years ago, when he observed the anniversary of the Tiananmen Square killings by delivering a vehement denunciation of the Chinese government's human rights record.
So it was 16 years ago when he was still dealing with his loss that he observed the personal trainers in his gym and the affect they were having on their clients.
Some of our observations parallel those made by Henry Fox Talbot 160 years ago when he made his first "photogenic drawings" on silver chloride containing paper.
That was seven years ago, when he was twenty-three.
Békésy's work had a profound impact on the field of middle-ear mechanics and bone conduction fifty years ago when he received his Nobel Prize.
