Epigenetic age oscillations in blood. (a–c) 24 h dynamics of epigenetic age predictions in WBC‐Neu dataset for Horvath pan‐tissue 2013 (a), Teschendorff epiTOC2 2020 (b), and Lu GrimAge2 2022 (c) clocks. Lines depict cosinor regression fits with solid lines indicating oscillation significance (cosinor p < 0.05). x‐axis: time of day; y‐axis: epigenetic age. (d) Estimated oscillation parameters of the 17 tested epigenetic clocks. Bold values indicate significant oscillations (p < 0.05), and asterisks indicate significance after Bonferroni correction for multiple testing. (e–g) Boxplots of epigenetic age predictions at two time points: 12:45 and 16:15 (Apsley et al., 2023) for Horvath pan‐tissue 2013 (e), Teschendorff epiTOC2 2020 (f), and Lu GrimAge2 2022 (g) clocks. Solid median lines indicate statistically significant differences (p < 0.05, paired Student's t‐test). x‐axis: time of day; y‐axis: epigenetic age. (h) Paired Student's t‐test p‐values and pairwise mean differences of epigenetic age between 12:45 and 16:15, matched by donor.