Although the longest day is December 21, the challenge could be taken up on any day in December or January.
Registration was free and easy. More than 5000 golfers signed up.
Shuker and Stuart were among them when they teed off at 5.30am on Saturday, December 19 on the Dannevirke Golf Club's course in perfect weather.
The course was in mint condition, ready for the regular competition later in the day.
Both play off 30 handicaps and they knew they were in for a tiring day but, armed with 36 golf balls, they set out.
Shuker said the first round went surprisingly well and the second was "pretty good", getting them into the clubhouse for lunch just as the regular field teed off about 11.30am.
Once the field was gone it was round three with lots of encouragement from family and friends and despite Stuart's sneaker blowing out the two made progress.
One concession was to stop scoring, which made the golf more relaxing.
They finished their fourth round before sunset at 6.30pm admitting the muscles were starting to tighten and looking for balls had become more cursory.
They still had a few balls left and the energy to make it to the local tavern for a celebratory and well-earned ale or two, both feeling very proud of their achievement.
Sunday was spent sleeping and recovering but both made it to work on Monday in "pretty good shape".
Shuker said the experience was exhausting and awesome and they were pleased to have completed the challenge successfully.
Before taking part in the challenge Shuker and Stuart had raised $1300, donated by family, friends and workmates.
After the event that had increased to around $3500, with the final figure to be confirmed.
As the Longest Day Challenge officially ends on January 31 there is still time for others to participate and to sponsor Shuker and Stuart.
Every donation goes towards cancer research, prevention and support services for people who need support the most.
To make a donation contact Chris Stuart on 021 233 4312 or Caleb Shuker on 027 349 8455.