If event histories are recorded in discrete intervals of times, errors are introduced when the data are converted from the unit in which they were recorded, such as date, to another unit such as age or duration. The problem is illustrated by the inconsistent age at marriage schedules published by two recent U.S. censuses. This paper develops a general method for fixing problems of this kind by using cubic spline interpolation. We use the method to adjust U.S. age at marriage data, thus resolving a large proportion of the discrepancy between 1960 and 1970 censuses.