Date Fields

Date fields are by default translated into an integer representing the elapsed time from a point in the past. The result of modeling dates will be binned groups of these integers. You can select bars in the Group Contribution Bar Chart and view linked charts to see the original dates in place of the integer encoding. You need to create a chart (such as a bar chart or summary sheet) on the date field if you do not already have such a display.

The date field may be encoded in other ways to make it more informative. One formulation is to convert dates into elapsed days from some common point in time. These can be calculated with the Expression Builder. One formulation is days in the past:

int(now - "date field")

This expression finds the number of days in the past that the date occurred. Note the conversion to an integer; otherwise the result will be a double with a fractional part showing fractions of a day.

Another formulation would use a known date in the past as the basis:

int("date field" - "01/15/1990")

Calculate elapsed days from the same start point, January 15, 1990.

You may be interested in exploring if events occur on a cyclic or periodic basis. To do this, create fields giving dates in terms of underlying cycles. These can be created with the Date Formatter. Possible fields are:

• Day of week
• Day of month
• Day of year
• Month of quarter
• Month of year
• Year
• Quarter