Dates as they are situated in the hierarchy of calendar time periods follow a pattern of a “contained-in” or subordinate relationship. It is possible to use the names and other features of identification of each of a time period’s superior to help identify the date. In record linkage this is called relationship matching. Figure 1 illlustrates how a day as the smallest time period is contained in a month and that in the year.
Thus there are two different kinds of records that may be linked. The date may be interpreted as a unique day in history. The scientific interpretation of a date is called the Julian day number. This number has been assigned by astronomers so as to be unique throughout all time. This linkage is illustrated in figure 2.
In order to perform calendrical record linkage the attributes of the respective time periods of the calendar to be matched are compared. The calendar time period may be supplied with identifiers that relate to it. This linkage is illustrated in figure 3. This comparison was not a successful match because of the disagreement in the day of the month (digit).
