This chapter deals with time series analysis and indices, focusing on how data series evolve over time. It introduces key concepts of price indices (e.g. Laspeyres, Paasche, Fisher) to measure price changes and adjust for inflation. Quantity and value indices, which are essential for understanding economic trends and real growth, are also covered. Techniques for shifting bases and chaining indices to maintain continuity in long-term data series are explained. Practical exercises are provided to apply these concepts to real-world scenarios.