Some data is captured at irregular intervals, including aerial imagery, power outages, and earthquakes. If you step the time slider through time at a regular interval, such as every 12 hours, you may experience periods of time when nothing is displayed in the map. One way to overcome this is to calculate an end time field where the time value for a particular feature is the start time value of the next feature. Run the Calculate End Time geoprocessing tool to calculate the end time field.
A feature with a start and end time is a feature valid for a certain duration. When visualizing your data using the time slider, the feature is displayed until the time on the slider is within the start and end time of the feature. For example, if the start time of a power outage polygon feature in your data is January 1, 2010, and the end time is January 15, 2010, the feature starts displaying as soon as the time slider's time is January 1, 2010. The polygon feature is displayed until January 15, 2010.
Another option for stepping through irregularly spaced temporal data is to configure the map's time slider to use the list of unique time values in a layer. The time slider displays the irregularly spaced information, such as tick marks, and you can step directly to the next or previous value. Set the layer or tables Time Interval property on the Properties dialog box to enable the View using unique times within the data option. In the Step group on the Time tab, choose the Layer option to have the time slider's step value offset display using the layer-defined property.
This option is only available if there are fewer than 1,000 unique time values in the layer. You can use a definition query on the layer to filter larger datasets to this limit as needed.