Mangawhai operates on a slightly different calendar to mainland Auckland. The Bothy closes at 1pm because the owner surfs. Salt & Pine doesn't open Mondays or Tuesdays. The Thursday Gallery is open exactly one day a week, and that day is Thursday. Knowing the rhythm saves you driving twenty minutes for a closed door.
The general shape
Most cafes are 7-day in summer (Dec–Feb), 5-day in winter (Mon–Tue closures common). Restaurants typically Thu–Sun in winter, Wed–Sun in summer. The market is Saturday year-round, smaller in winter. Beaches are 24/7, just colder.
The off-season honesty
May–August, more places are closed than open on a given Tuesday. That's a feature for locals (we get our village back) and a frustration for visitors. Plan around it: arrive Thursday or Friday for the better selection of open kitchens.