Every New Year since 2003 Gisborne's population swells, as much as doubling in size as tens of thousands of partygoers flock in from out of town for Rhythm and Vines.
A Kiwi partying rite of passage, you'd be hard pressed to find anyone under the age of 35 who hasn't gone to "RnV" at least once.
And the good times - which feature, along with the gig's troubled times, in the New Zealand Herald documentary series The Road to Rhythm - extend beyond those with a ticket.
Every year the festival injects about $12 million into the local economy according to the region's most recent economic impact report, taken in 2010.
Comparatively, a slew of summer of festivals including Adele and Justin Bieber brought in an estimated $37.7 million for Auckland in 2017, and Ed Sheeran's Dunedin shows were tipped to net the city $34m.
In 2011, the Rugby World Cup attracted $573m to New Zealand's economy as a whole and in February this year the Sevens' tournament weekend alone stimulated an extra $1.9m in spending, part of an estimated $5m boost the event would bring to the local economy overall.
Unlike big one-off events, Rhythm and Vines is a staple, a reliable boon for local business in late December and early January.
Mayor Meng Foon reckons each festivalgoer spends between $600 and $100 each, 80 per cent of which he estimates lands back in the pocket of Gisborne locals.
"You've got your festival tickets, you've got your food, you've got your beverages, your camping or glamping or staying in homes, you've got your fuel," Foon said.
"Even the $2 shops where they buy all their ponchos when it rains [benefit]."
The region's exposure through media coverage was akin to free tourism advertising and local organisations like St John paramedics and the waste management team benefited by taking on contracts with the festival itself, Foon said.
The New Year period attracted about 35,000 people to Gisborne each year.
Last year 20,000 of those were Rhythm and Vines ticket holders.
"In the city we have about 35,000 people so our population doubles - it's fantastic."
Since the festival's inception 15 years ago, Gisborne's tourism industry had responded to growing numbers and an increase in interest in visiting the region generally.
"It's got coffee shops now - you can get a latte in Gisborne," Foon said.
Some former festivalgoers were even moving to the region after starting a family because they liked the place so much.
"And the introduction to Gisborne was Rhythm and Vines, I've heard several stories like that," Gisborne Chamber of Commerce chief executive Terry Sheldrake said.
"It's huge for our region. And nothing but positive vibes from the chamber for it."
Every year the festival brought a "thriving buzz" to the community.
"Economically a lot of businesses, typically your restaurants service stations, do well but it goes wider.
"Community groups raise funds from working across Rhythm and Vines and huge credit to the organisers, it certainly has legs as an event."
Adam Hughes is the general manager for tourism at Activate Tairawhiti, an economic development agency for the region.
"There's undoubtedly a large economic impact on the region from the festival," Hughes said.
"The peak is about three days long where it completely changes the [make-up] of the city. They are unmissable."
>> Watch the The Road to Rhythm series at www.nzherald.co.nz