We create mental maps of the space that surrounds us; our brains also compute time – in particular, the time of the day! Visual, thermal, social and other cues tune the clock-like timekeeper. As a result, the internal clock synchronizes with the external day-night cycles. Remarkably, daylength itself varies, causing the change of seasons and forcing our brain clock to accommodate layers of plasticity. But the core of the clock, i.e., its molecular underpinnings are highly resistant to perturbations, while the way animals adapt to the daily and annual time shows tremendous biological diversity! How can this be achieved? We will focus on 20 pairs of clock neurons in the Drosophila brain to understand how a small neural network perceives and responds to the time of the day, and the time of the year.