I successfully imported a shapefile that uses the time slider in ArcGIS Desktop with no problem. However, when I bring that same data into Explorer online, the time slider option does not show up. Any suggestions on what I need to do to make this work?
So, I don't have an answer to your question. But, could you give me some hints on how you set up the time enabled data? I have water quality stations that are sampled weekly and would like to show the changes over time. Thanks, and sorry I can't help you with your question.
If you add a time-enabled service to ArcGIS Explorer Online, for example http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Hurricanes/NOAA_Tracks_1851_2007/MapServe..., then the time slider will be shown automatically in your map. However I'm afraid the time slider doesnt work on imported layers currently - the dates are treated as an attribute field; this is like adding a map service that has date attributes, but it not actually time-enabled. I think this is a good enhancement to suggest over at ideas.arcgis.com.
To make it work in ArcGIS desktop, follow the instructions in the Help file for enabling time-dependent layers. Based on the response above, there doesn't appear to be a way to do in ArcGIS Explorer Online using a shapefile, though if your data resides on a server, you can probably make it work. I can't help there because I don't work within a server framework.
Melissa, is it your data? This is the help location for time-aware layers for ArcGIS Server. If it's not yours, you might want to contact the organization hosting the data and see if they can modify it.