Changes in social zeitgebers across the lifespan affect the interaction between biological and social clocks, potentially contributing to social jetlag. Extant literature suggests a reduction in social jetlag given declining social obligations occurring after retirement, but is limited to self-reported methods and cross-sectional designs. Leveraging longitudinal and ecologically valid data from consumer sleep technology, we analysed objective sleep data from 2439 users of the polysomnography-validated SleepScore mobile application, encompassing 500,415 total nights recorded. We examined the relationship between age as a continuous variable, age as a proxy for retirement status, and social jetlag. Additional linear models were employed to assess the effect of self-reported chronotype, average reported daily caffeine, alcohol and stress on social jetlag. There was a significant negative association between overall age and social jetlag (β = −0.64, t = −9.90, p < 0.001, effect size = 0.040), such that every 1-year increase in age corresponded with a 0.64-min reduction in social jetlag. The inclusion of self-reported chronotype, stress, caffeine and alcohol increased the explanatory power of our models slightly, but the effect of age remained consistent (β = −0.642, t = −8.91, p < 0.001, effect size = 0.046). Retirement-aged individuals exhibited nearly 50% less reduction in social jetlag than pre-retirement (30.6 ± 48.2 min versus post-retirement: 15.8 ± 41.6 min, p < 0.0001). While social jetlag after retirement was most pronounced for strong evening chronotypes (β = −0.41, t = −2.876, p = 0.004, effect size = −0.4276), pairwise comparisons revealed no statistically significant differences in the slopes between chronotypes (p > 0.05). Thus, social jetlag decreases across the lifespan, and its reduction appears to be amplified post-retirement even after accounting for behavioural factors.