語言地理學藉由分析語言特徵的地理分布，推斷地域變體的歷時演變跟造成變化的原因，善加運用可以處理語言史的不連續性。海陸客家話“明天”說[Sau¥¥ tso⁄‹]，首字語源不明，學界近來往往寫做「韶」。我們透過語言地理學的研究得到以下結論：客家話「明天」的說法呈環狀分佈，創新形式「天光（日）」在最內側，較古老的「明＋X」（X 以「朝」或「晡」為主）在最外圍，「晨＋X」（X 多數為「朝」）類、SHAU 類、SHA 類介乎其中。根據地域連續性的原則我們可以推斷，「韶」（聲調有陰平、陽平、上聲）本是「晨朝」的合音。

In this paper we investigate a part of the history of Hakka dialects using a geographical approach. The word ‘tomorrow’ in Taiwanese Hailu Hakka is [Sau¥¥ tso⁄‹], of which the first syllable is of unknown origin. The geographic distribution pattern of ‘tomorrow’ of the Hakka spoken in the Fujian, Guangdong, and Jiangxi provinces shows three concentric circles. The most recent innovation 天光( 日）is in the center; the older expression, 明＋X, is distributed along the most peripheral region; and the 晨＋X, SHAU-, and SHA- forms are scattered between the other two areas. Judging from the spatial continuity principle, we conclude that SHAU- is derived from a contraction of 晨朝.