The intensive use of daylight in buildings is beneficial at many levels: it provides sufficient levels of illumination to perform working activities throughout the day and it reduces the use of artificial light, which in turn leads to lower electricity consumption [1-3]. The spectral composition of daylight often leads to higher visual comfort in humans, compared to electric lighting. There are also illuminance and spectrally-dependent light effects on the human circadian system, which regulate hormonal rhythms, alertness and (visual) performance across 24 hours [4-6]. The main objective of this work was to assess luminous performance in office buildings and to test optimizations by virtually applying different daylighting strategies by computer simulations.We first assessed the daylight distribution in two different office rooms, set-up as test modules on the EPFL campus in Lausanne (46° 32'N, 6° 39'E). One of these test modules is equipped with a standard double-glazing; the second one comprises anidolic daylighting systems [7], which convey diffuse daylight and sunlight deeper in the room, and reduce glare risk. In both rooms, we also assessed vertical spectral irradiance in the visible range, which gave us additional information with respect to photo biological properties of the available daylight. We then measured the real daylighting situation in an office room located in the city of Zacatecas, Mexico (22°47'N 102°34'W), which is equipped with a standard double-glazing window. In a next step we tested, whether the daylight distribution for this room could be improved by virtually applying different complex fenestration systems (such as prismatic panels and laser cut panels) by using computer simulations. The results of these simulations showed higher indoor luminous performance with the two advanced daylighting systems. This new method may contribute to an improved and tailored design of daylight availability in real buildings at different geographical locations.