How To: Specify the current date as the default value for a Date field when creating new features in ArcMap
Instructions provided describe how to specify 'today's date' as the default value for a Date field when creating new features.
Although it is not possible to dynamically auto-populate a Date field with the current date for each newly created feature, it is possible to specify the date a feature was created manually by changing the Date field's default value inside of a feature's Template Properties dialog box.
Right-click the desired layer in the Table of Contents (TOC) and click Open Attribute Table.
Select the Table Options drop-down and click Add Field.
Name the field 'DATE_MOD', select the field type Date and click OK.
Right-click the layer in the TOC once more and click Edit Features > Start Editing.
Once the Create Features window appears, right-click the feature template for the desired layer and click Properties.
Click the <Null> value next to the Date field and choose today's date from the calendar drop-down. Click Apply and OK.