Workers now have more rights to rest and meal breaks than they had on Sunday.
The changes, which passed into law in December and came into force on Monday, largely overturn changes the previous National-led Government made in 2014, which came into force in March 2015.
National's changes took away workers' rights to have rest and meal breaks at regular intervals through their shifts, instead making it "at the times and for the duration agreed between the employee and his or her employer".
If no agreement was reached, the law said the breaks only had to be "at the reasonable times and for the reasonable duration specified by the employer".
Bosses didn't have to let workers have breaks if they could not "reasonably provide the employee with rest breaks and meal breaks", as long as the employee was reasonably compensated. And there was no minimum length of time set in the legislation that bosses had to give their employees off.
The justification was to give both employers and employees more flexibility, but was criticised by unions and Labour as being biased towards the interests of employers.
The new rules
Monday's changes don't take away the ability of bosses and employees to agree on when rest and meal breaks can be taken, or how long they are.
But if they can't agree, the new legislation tips the balance in favour of the employee - outlining what they're entitled to as a bare minimum.
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Between two and four hours of work, employees are entitled to a paid 10-minute break in the middle of their shift. Between four and six hours, they're entitled to a paid 10-minute break after a third of their shift, and an unpaid 30-minute meal break after two-thirds.
For a typical eight-hour day, workers are entitled to two paid 10-minute breaks either side of a 30-minute unpaid meal break.
The only exceptions are if they're "engaged in an essential service"or national security depends on the employee not taking a break at that particular time, and they can't be replaced at reasonable cost. If that's the case, the employer must either give the employee the equivalent time off or pay them for the extra work.
If their pay is variable, it has to be at least the average rate they normally get.
"Many of the changes are familiar to employers, as they roll the law back to how it was as recently as 2015," the Ministry of Business, Innovation and Employment (MBIE) says on its site.
MBIE guidelines say both parties should negotiate in good faith, and mediation services are available if discussions break down.
Employers who fail to give their workers the minimum breaks they're entitled to can face penalties.