Carbon dots, a young member of the carbon nanomaterial family, are quasi-spherical nanoparticles, which have fluorescent properties as their key characteristic. A wide range of starting materials and synthetic routes have been reported in the literature, divided into two main categories: a top-down and bottom-up approach. Moreover, a series of different parameters that affect the properties of carbon dots have been investigated, including temperature, starting pH, as well as precursor concentration. However, the effect of reaction time has not been extensively monitored. In our study, a biomass derivative was treated hydrothermally with varying reaction times to draw a solid formation mechanism. In addition, we monitored the effect of reaction time on optical and structural characteristics, as well as the chemical composition of our materials. Our key findings include a four-stage formation mechanism, a higher level of crystallinity, and an increasing brightness over reaction time.