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I've got a layer of polygons where each has a date associated with it. I want to color the polygons with graduated colors, but I want the colors to start with the newest polygons and fade to the oldest polygons. So far I haven't been able to find a way to do this in ArcMap (<= 9.3.1) other than to create a new field and calculate some integer or float value based on the date. Is it possible to use a date or time field directly?

  • The data is natively a date-time value
  • There are far too many records to use any unique-value renderer
  • Converting the date to a numerical field is an answer for a different question.
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I beleive range classification in Arcmap only works with numeric values but I could be wrong. –  badkins Apr 7 '11 at 12:10

5 Answers 5

If you are looking for Quantities -> Graduated Colors/Symbols, they won't directly work with Date fields. You could however convert the date fields to numbers and use that instead. I'd convert each date to an Epoch timestamp (number of seconds since a particular date, 01/01/1970 being used most frequently), then use the Epoch timestamp to symbolize your features.

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Upvote. Good suggestion. I use this method a lot. If you use a larger numeric value type you can use a wider range of dates in some systems. –  Glenn Apr 7 '11 at 15:07

Convert Time Field (Data Management)

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//0017000000v2000000.htm

Then use Time Animation

enter image description here

Then you can symbolize your data

Video http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=Change_in_cropland_over_time

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The data is already in a time field, and unfortunately I don't have ArcGIS 10 to work with; however, is your method only for animations or will it allow one to symbolize a static map based on the date? –  dmsnell Apr 8 '11 at 16:38

I had the same question, and found myself here.

What I did is set a definition query to control the max date, date< '2009-01-01 00:00:00'

Then I can group the unique value symbology for anything pre-2009.

Then go back to the def query, extend the date range: date< '2009-01-01 00:00:00'

go back to symbology, add values and group.

repeat this process.

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I'm not sure what version of ArcMap you are using, but with 9.3.1 if you go to the layer>Properties>Symbology tab, then select Categories>Unique values, and select your date field in the Value Field drop down. Next, select all of your date values using the shift key and pick a graduated color ramp in the Color Ramp dropdown. Yes, you cannot set a specific classification (e.g. Quantile) on your date field; however you can still symbolize your features in a graduated color fashion.

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I created a table in Excel that had dates between 1/1/1901 and 12/31/2101 that can be joined to a standard date value (no time portion of a date). The table has 4 columns that convert the date to numeric values of the Year (1901-2101), the Month (1-12), Year with Decimal Month ((Month - 1) / 12), Year with Decimal Day of the Year (Day of the Year at midnight / total days in the year).

I imported that table into ArcGIS as a File Geodatabase table. Excel dates cannot be any earlier than 1/1/1900 and I needed dates extending back to 1890. To deal with that I copied records between 1/1/2090 and 12/31/2101 (so leap years would align) to a new table and subtracted 200 from the year component of the date and did a similar adjustment to the other date values. Then I appended the original excel import to this new table so the dates would have ordered ObjectIDs.

This table can be joined to feature classes that cannot have their schema modified. Additionally, by joining this table to the date I want to symbolize I can be sure that all dates possible in that date range will be accounted for in the symbology, even if they are not currently present in the data. The numeric values in any of the 4 fields can be used with Quantity style symbology without maintaining a separately calculated field. I can use Categorized Symbology with the Year or Month fields if I want (although I would have to add values not actually in the data in this case) and I do not have to maintain a separate field in the feature layers being symbolized that has to be separately recalculated prior to redrawing.

Other fields could be added to the separate date table easily, like day of the year whole numbers, or numbers/strings showing the YYYYMMDD style of date for sorting, to support any other symbol groupings by date that may be required without constantly modifying each separate feature class.

If I did take the separately calculated field in each feature class approach, I would use Attribute Assistant to create a DynamicValues table rule that would maintain the field value during editing.

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