Abstarct: The present study aims to profoundly analyze calendar anomalies in the Tehran Stock Exchange (TSE) and to elucidate the behavioral dynamics of traders within the frxamework of the Adaptive Markets Hypothesis (AMH). To this end, the behavior of six key market indices (the Overall Index, Iran Fara Bourse (IFB) Overall Index, Industry Index, First Market Index, Second Market Index, and Top 50 Companies Index) was examined over the period from December 2008 to March 2025 to identify the impact of biological calendars and cultural structures on market efficiency. The anomalies investigated in this research include the holy month of Ramadan, the weekend effect, the last week of the Iranian calendar year (Esfand), the Nowruz holidays, and the month of Muharram. Utilizing GARCH-family volatility models and Markov Switching models, it was determined that efficiency in the TSE is not a static and absolute characteristic, but rather a cyclical and contingent variable. The research findings indicate that during periods such as the holy month of Ramadan, the first decade of Muharram, and the eve of the Nowruz holidays, the market witnesses a significant transition between different regimes of return and volatility. Furthermore, the results show that calendar anomalies in large-cap companies (Top 50 Companies Index) are adjusted more rapidly and sustainably compared to the general body of the market, indicating a higher relative efficiency in this segment. By empirically validating the Adaptive Markets Hypothesis, this study proves that traders in the Iranian capital market are adaptable agents who align their strategies with collective beliefs, liquidity necessities, and temporal cycles.