Lovers of Canada's national parks are celebrating the country's 150th birthday a little earlier than most after purchasing park passes and realizing they don't expire until 2018.

It's part of an initiative brought in by the Liberal government that will make park access free for all users in 2017 and for youth and new Canadians starting in 2018.

Catherine McKenna, the minister of the environment and climate change, who's responsible for overseeing Canada's parks, had the plan laid out in her ministerial mandate letter.

"Make admission for all visitors to National Parks free in 2017, the 150th anniversary of Confederation," reads the letter. "Beginning in 2018, ensure that admission for children under 18 is free, and provide any adult who has become a Canadian citizen in the previous 12 months one year's free admission."

Park pass purchasers received a notice informing them the pass would technically be good for two years. (CBC)

Darren Reeder, the executive director of the Banff Lake Louise Hospitality Association, says he's excited by the move.

"I think the experience will be an exceptional one, particularly for many new Canadians who have yet to experience our national parks," he said.

"It's a great way to introduce those who have yet to visit a park and those who have maybe lost familiarity with our parks, to reconnect."

Most funding for Parks Canada's roughly $670-million annual budget comes from the federal government, but the agency also generates its own revenue from a variety of sources, including entrance fees, camping and recreation fees, rentals and concessions.

Entrance fees totalled about $59 million — half of Parks Canada's non-government revenue — according to the agency's 2014 annual report.