A change to the provisional calendar was the source of the difficulties, with the Australian season opener moving three weeks forward to its now-confirmed date of March 20 - leaving McLaren (and no doubt a number of their rivals) scrambling to adjust their schedule.
"Our entire build programme wasn't lined up for that!" McLaren's operations director Simon Roberts told the team's website. "So we knew we had a problem to solve. In terms of our design and engineering capacity, it's a relatively straightforward re-planning exercise - there's less time to get the work done, so everyone works a bit harder.
"But the build schedule is on a critical path - it needs to pass all the FIA safety tests and be ready for the first test, which was also brought forward. In that situation, you can't just re-plan, you need to do something different."
Roberts explained that the only solution was for some staff to sacrifice their winter break. "In simple terms, we put about eight shifts of work back into the programme over a five-day period - a fantastic effort. In total, there were about 110 people involved and we looked after our Christmas workers with a competitive package.
"We had a really good response, and people seemed to enjoy it too – it was a bit weird, not having all the time off, but there was a good spirit in the place. Everyone knew why they were doing it, and it really cleared the decks.
"Most pleasingly, it meant that, once we came back in the New Year, we were back on schedule – and it felt like the programme had always been phased that way. It was an incredible effort."
McLaren announced on Monday that their 2016 car, the MP4-31, will be revealed on February 21, the day before the first test begins in Barcelona.
Sauber, meanwhile, confirmed that their new car will not be ready until the second pre-season test, also in Barcelona, on March 1-4. The team will therefore run last year's car, but in 2016 branding, at the first session.