"I don't think it was just to the benefit of gay men ... but to anyone who stands for openness.
"It changed New Zealand, I think, and that was the point of opponents. They were right, it did make for a big change in the way we view sex, and I think that's a very good thing."
The Homosexual Law Reform Bill, sponsored by former Labour MP Fran Wilde, passed on July 9, 1986 after an intense and divisive debate.
Mr Logan gave up his business, a bookshop, to work for the Gay Task Force. He was abused on the street, got malicious calls and a bottle was thrown at the house he was believed to be staying in.
The debate bought to the surface a secret way of life and not everyone in New Zealand was ready for it.
"Very few gay men or lesbians felt they could be open about themselves with any more than a few friends in those days so homosexuality was forced to be very secret and very invisible.
"Gay people and lesbians lived with a lot of fear that they would be exposed."
Efforts for change through "respectable liberal tactics" with younger gay lib activism finally came to a head with the bill in 1984.
"That triggered an enormous public debate - in some ways much more important than the law change was the public debate."
No corner of the country avoided it.
"There was this incredible upsurge of discussion and people came out in their thousands to their families, to their workmates, in sports teams even, and so it was something that was discussed in newspapers and pubs and on television every day."
It was an exciting time but was also fraught with danger.
"People felt under scrutiny and it was a very difficult time in lots of ways but at the same time there was public discussion which led to a great deal more understanding."
The debate was held at a time of phobia around Aids which had just become a serious and public problem - 24 people Mr Logan knew died of the disease between 1985 and 1990.
"At the same time that we were having this campaign our friends were dying."
One setback for the movement was the failure of a vote to include discrimination based on sexuality under human rights legislation.
"It did seem a terrible defeat that we'd lost that and that was demoralising."
The feeling was politicians were trying to "have a bob each way".
"[They were] trying to send a message to their electorates that they weren't all that liberal, it was what they saw as their necessary vote in order to be able to vote in favour of the second part of the bill which was the criminal law."
But in the end the bill passed.
"I was in the gallery of the house with my partner - yeah [I felt] huge exhilaration and elation. It was wonderful ... you don't get many of those kind of victories in life."
Opposing the reform then - and now - was the Society for the Promotion of Community Standards and its vocal frontwoman, Patricia Bartlett.
The Salvation Army was also staunch in its opposition but that stance has softened over time. Its policy now is not to oppose the legality of homosexuality but to continue to consider it immoral.
Commissioner Garth McKenzie, territorial commander, said it regretted the hurt the Salvation Army's official opposition to the reform bill caused.
"We regret any hurt that may remain from that turbulent time and hope to rebuild bridges of understanding and dialogue between our movement and the gay community," he said.
"We may not agree on all issues, but we can respect and care for one another despite this."
Meanwhile, Mr Logan, now a counsellor and celebrant living in Mt Victoria with partner Rangimoana Taylor, is looking forward to partying this weekend.
Events to mark the occasion include an exhibition of photos on the issue at Turnbull House and a reception at Premier House.
MP's bill lays the ground for next big battle
Bill Logan and his colleagues are facing a new battle - gay adoption.
Green MP Metiria Turei has drafted a member's bill to allow gay and lesbian couples to adopt. When The Adoption (Equity) Amendment Bill is drawn from the ballot is up to chance but Ms Turei says it is overdue.
"It's a major hole in the law that's unnecessary and needs to be filled."
The law allows married people and single people including single gay and lesbian people to adopt but bans gay and lesbian couples.
"In some ways it's a very small legislative hole but it has big impacts for gay and lesbian couples and there's no policy reason at all why it shouldn't be filled, it's just that none of the other political parties have had the gumption to do it," said Ms Turei.
It's a battle Mr Logan thinks will be straightforward.
"I think gay adoption is important but I think it must go through," he said. "There is something bizarre about a world which doesn't give obviously perfectly adequate parents the right to be parents."
He expects the same arguments as those in the recent civil unions debate to be raised.
"It will generate the same kind of debate but gradually people understand the issues better."
A bigger concern to him was bullying in schools, where anyone who did not conform to a stereotype was targeted.