In wireless networks formed of battery-powered nodes, energy consumption is a major concern. On the communication side, energy can be saved by switching transceivers to idle or power-down mode when not needed. To this end, duty cycling protocols located at medium access control level have been devised. These protocols have in common that they define modified carrier sense multiple access with collision avoidance schemes and that they assume the availability of some time synchronization mechanism. This strongly limits their potential to reduce energy consumption, as well as their flexibility regarding activity phases. In this paper, we propose a more flexible and energy-efficient solution for duty cycling, which is based on our experimental wireless medium access control protocol MacZ. Flexibility is strengthened by the possibility to define weakly periodic activity periods. Energy efficiency is improved by the possibility to assign exclusive transmission slots, thereby switching transceivers to active mode only when needed. Both measures are supported by an underlying protocol for accurate, deterministic tick and time synchronization. We assess our solution and compare it to well-known duty cycling protocols on the basis of real-life scenarios. Copyright © 2012 John Wiley & Sons, Ltd.