Background: Aneurysmal subarachnoid hemorrhage (alpha SAH) is an acute and sometimes fatal cerebrovascular disease. The chronobiological patterns of alpha SAH are still unclear worldwide. This 15-year time-series study aims to clarify the chronobiological patterns including seasonal, monthly, weekly, and circadian distributions of alpha SAH. Methods: We retrospectively analyzed the medical records of aSAH patients in central China. To investigate seasonal and weekly distributions, we used the chi(2) goodness-offit test to analyze the uniformity of the onset time. To explore monthly and circadian distributions, we established Fourier models to show the rhythmicity in chronobiological patterns. Subgroup analyses were conducted to assess the impact of age, gender, hypertension statuses, and aneurysmal characteristics (number, size, and location) on the chronobiological patterns of alpha SAH. Results: A total of 1469 patients with alpha SAH were recruited in the study. The seasonal and monthly distribution exhibited significantly higher incidence in winter and January/December and lower incidence in summer and July. The weekly distribution of alpha SAH onset showed no significant uneven variation. The circadian distribution of alpha SAH exhibited a significant pattern (p = 0.0145), with a morning peak around 8:00. and a late afternoon peak at 16:00-20.00. The circadian rhythmicity varied in subgroups of different ages, genders, and aneurysmal locations. Conclusion: The occurrence of alpha SAH exhibits significant circannual and circadian patterns among the Chinese population. Patients with alpha SAH of different ages, genders, and aneurysmal locations would present different chronobiological patterns.