Today, Tomorrow, and Overmorrow: The Acquisition of Deictic Temporal Terms in English and German

English and German both have single words for yesterday and tomorrow, but German also includes the words vorgestern ("the day before yesterday") and übermorgen ("the day after tomorrow"). This study investigates how these differences in time-word sets influence children's learning of temporal language. In two tasks, English- and German-speaking children ages 3 to 7 (N = 304) and adult controls (N = 75), marked the locations of temporal terms on a continuous timeline and a discontinuous calendar template. We assessed knowledge of three distinct facets of time-meaning (past/future status, sequential ordering, and temporal remoteness) and precise meanings for temporal terms. Our results show that German-speaking children were more likely to demonstrate precise understanding of items lexicalized only in German (e.g., übermorgen/day-after-tomorrow) as well as basic time words lexicalized in both languages (e.g., gestern/yesterday). The German advantage was primarily driven by children's better understanding of these words' temporal remoteness (i.e., distance from the present), while there were no language-group differences in children's understanding of past/future status. These findings suggest that children acquire time-word meanings gradually, using different linguistic cues for different facets of meaning, and that having a more extensive time-word lexicon may help constrain German-speaking children's early understanding of temporal concepts like yesterday and tomorrow.