We shifted our wall clocks to Daylight Saving Time, and it took "minus one hour" to achieve that. But how long does it take the human body to adjust the biological clock? It turns out that a walk outside can help a lot to accelerate to transition, provided that yo do that at the right time of day. But of course, in the LoLiPoP-IoT project, the question also is "How can a Healthy Building help to smoothen the transition?" Using today's models on circadian rhythm, at Eindhoven University of Technology we calculated the effects.