Hi Nicole,
The Time Slider control requires that the geometries are on the client in order to work, so a Feature Layer is required.
If you wanted to do this with a Dynamic Map Service layer you'd have to create your own slider control and use it in conjunction with a Query Task to retrieve the features from the Server and symbolise on the Graphics Layer ... which is basically what the Feature Layer is doing on your behalf!
If you insist on having the features rendered Server-side, you could apply layer definitions to the Dynamic Map Service layer, but either of these methods could become very 'chatty'.
Is there any reason why you don't want to use a Feature Layer? You don't need to do anything special to set it up - just create one from an existing layer in your Dynamic Map Service.
HTH? Or am I missing something?
Best regards,
Mark Lewin