Background: Digit preferences are normally seen as potentially harmful biases in respondents' reports. Possibly such preferences might also be the cause of some patterns found in Swedish marriage formation, thus affecting actual demographic behavior. Objective: Digit preferences in marriage formation in Sweden are examined − more specifically, the additional propensity to marry for the first time during the year 2000 or at ages ending with 0 − and their demographic and socioeconomic correlates. Methods: Event-history analyses are applied to Swedish register data covering 3.5 million men and women in 1991−2007. Results: First-marriage risks clearly increase for both men and women at exact ages 30, 40, 50, and 60 and in the year 2000. These patterns exist across demographic and socioeconomic groups and are not due to measurement error or random variation. Conclusions: The timing of marriage is not strictly determined by conventional demographic or socioeconomic factors. Whether the findings are idiosyncratic to contexts like the Swedish, where there are small differences between marriage and cohabitation, remains to be answered.