Mr Johnstone was not sure whether it was his favourite meals, sausages and roast, which preserved his health — but it was certainly the "luck of the draw", he said.
He was born on November 16, 1918, in the small Southland town of Drummond to parents Eliza and Jack.
"I was told I would not live long. I had the whooping cough, but I guess I came right."
He still felt like a child at heart despite his age, and his 104th birthday was just another day.
"I did more celebrating when I was young, so I don’t bother too much nowadays.
"I guess I’ve got no other option but to grow older."
He had fond memories of growing up in Drummond as the youngest child of four.
"I had two older brothers and a sister ... and it was a country district — there was a grocery store, a school, a church, a hotel and a town hall, and that was it."
He began school at age 3, and finished his schooling at 13.
As a teenager he lived an ordinary life.
"In our days, there wasn’t much money around. You had to catch a few rabbits, and the lorry would come around and pick them up for 3 pennies.
"I remember for me, once I’d sold my rabbits I’d go and buy a packet of chewing gum."
He would lend a hand to neighbouring farmers and helped with a range of jobs including harvesting and stocking oats.
"I enjoyed working with the animals and the people."
From 1942 to 1945, he served as a gunner in World War 2 as part of the 29th Battery of the 6th New Zealand Field Regiment Head Quarters in Italy.
When he returned from the war he went back to farming until he retired at 76 and moved to Winton in 1995.
He never married or had children but kept busy with sports, watching horse racing, attending socials and being involved in the community.
"Every day was much the same but I’ve had a happy life.
"I wasn’t a traveller, I never went travelling the world, but I enjoyed being a part of the community."
