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

English and German both have single words for <i>yesterday</i> and <i>tomorrow</i>, but German also includes the words <i>vorgestern</i> ("the day before yesterday") and <i>übermorgen</i> ("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 (<i>N</i> = 304) and adult controls (<i>N</i> = 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., <i>übermorgen</i>/<i>day-after-tomorrow)</i> as well as basic time words lexicalized in both languages (e.g., <i>gestern</i>/<i>yesterday</i>). 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 <i>yesterday</i> and <i>tomorrow</i>.