This paper examines how Buddhist preachers in late medieval China expanded the meaning of the temporal register of an oft-used phrase “[at] one time” (Ch. yishi 一時, Skt. ekasmin samaye, Pāli ekaṃ samayaṃ) in the opening formula of Buddhist scriptures. Through an analysis of the “sutra lecture texts” (jiangjingwen 講經文) found in the Dunhuang manuscripts, this study explores how these preachers broadened the interpretation of “[at] one time” to encompass a wider transtemporal and transhistorical context. During their popular sutra lectures for the laity, Buddhist preachers emphasized the synchronicity of preaching, hearing, and enlightenment, drawing upon the concept of “sympathetic resonance” (ganying 感應) from Chinese indigenous cosmology. By using metaphors and analogies, the preachers interpreted “[at] one time” as any moment when a teacher imparts the Dharma and a disciple receives it, thereby surpassing the constraints of a specific historical setting. Ultimately, this paper argues that through their imaginative and skillful oratory, the Buddhist preachers in late medieval China transposed the scriptural concepts of “[at] one time” and “Dharma-realm” to the present moment of preaching, thus transforming timely preaching into a timeless practice aimed at facilitating the salvation of their audience.