If event history data are recorded in discrete intervals of time, 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 general method for treating problems of this type using cubic spline interpolation. The method is used to adjust U.S. age at marriage schedules, explaining a substantial part of the discrepancy in the 1960 and 1970 censuses.