This paper discusses significant developments in the radiocarbon calibration program, OxCal. Key advancements include improvements to the calibration algorithms, particularly in handling multiple phases and mixed calibration curves. The new algorithms better account for variability in calibration curve errors and allow for the mixing of different calibration curves, such as marine and terrestrial sources in human bone analysis. The Bayesian analysis procedures have been enhanced to better handle the grouping of events using *boundaries*, ensuring that the span of the timescale is treated uniformly. The Markov Chain Monte Carlo (MCMC) sampling has been improved with a fully floating-point algorithm and the integration of the Metropolis-Hastings algorithm, leading to faster convergence for complex models. Additionally, the program now provides tools for better convergence testing, including the ability to include convergence data in plots. The paper also outlines methods for testing the program's performance, such as simulated dating and effective prior analysis, to ensure its reliability and accuracy. Overall, these developments have significantly enhanced the usability and reliability of OxCal for radiocarbon dating and chronological analysis.This paper discusses significant developments in the radiocarbon calibration program, OxCal. Key advancements include improvements to the calibration algorithms, particularly in handling multiple phases and mixed calibration curves. The new algorithms better account for variability in calibration curve errors and allow for the mixing of different calibration curves, such as marine and terrestrial sources in human bone analysis. The Bayesian analysis procedures have been enhanced to better handle the grouping of events using *boundaries*, ensuring that the span of the timescale is treated uniformly. The Markov Chain Monte Carlo (MCMC) sampling has been improved with a fully floating-point algorithm and the integration of the Metropolis-Hastings algorithm, leading to faster convergence for complex models. Additionally, the program now provides tools for better convergence testing, including the ability to include convergence data in plots. The paper also outlines methods for testing the program's performance, such as simulated dating and effective prior analysis, to ensure its reliability and accuracy. Overall, these developments have significantly enhanced the usability and reliability of OxCal for radiocarbon dating and chronological analysis.