The bloodstains age estimation (BAE) is an essential sub-discipline of forensic science, particularly within the context of bloodstain pattern analysis. Over the past three centuries, multiple methods have been developed for BAE with Ultraviolet-visible (UV-Vis) spectroscopy emerging as one of the most prominent due to the chromatic properties of blood. This article provides a comprehensive review of the detection and elucidation of age-related color changes and the methods for estimating the age of bloodstains based on these changes. It begins with a brief overview of existing BAE methods, then presents the principles of UV-Vis spectroscopy and the chemical changes in hemoglobin that enable accurate BAE with this method. After that key publications from late 18th century studies to recent innovations are reviewed. The review also explores the various external factors influencing the aging process of bloodstains and how these factors have been addressed in forensic research.