The 'arrow of time,' a concept first introduced by Sir Arthur Eddington, reflects the one-way flow of time and its association with various physical asymmetries in thermodynamics, cosmology, quantum mechanics, field theories, and beyond. Yet, the foundations of the arrow of time continues to challenge physicists and philosophers, having profound implications across multiple theories and disciplines.This volume compiles insights from the international colloquium 'The Arrow of Time: From Local Systems to the Whole Univers' held in Buenos Aires in 2023. It explores diverse perspectives on the arrow of time in thermodynamics, quantum mechanics and cosmology, its relation to counterfactual reasoning, free will and the growing-block universe, the interplay between consciousness and time, and the implications of time-reversal invariance. Collectively, these contributions provide a rigorous and comprehensive analysis of the enduring enigma of time's unidirectional nature.