Circadian rhythms in physiology and behaviour have near 24h periodicities that must adjust to the exact 24h geophysical cycles on earth to ensure adaptive daily timing. Such adjustment is called entrainment. One major mode of entrainment is via the continuous modulation of circadian period by the prolonged presence of light. Although Drosophila melanogaster is a prominent insect model of chronobiology, there is little evidence for such continuous effects of light in the species. In this talk, I will describe my research demonstrating the effects of prolonged light exposure at specific times of the day on the timing of sleep/activity rhythms. Further, I will discuss results that show that certain spectral compositions of light lengthen the circadian period of Drosophila and provide evidence that this is produced by the combined action of multiple photoreceptors which includes the cell-autonomous photoreceptor cryptochrome. Finally, I introduce ramped light cycles as an entrainment paradigm that produces light entrainment that lacks the large light-driven startle responses typically displayed by flies and requires multiple days for entrainment to shifted cycles. These features are reminiscent of entrainment in mammalian models systems and make possible new experimental approaches to understanding the comparative mechanisms underlying timing of sleep rhythms in the fly.