Good idea!
When I try setting the identify parameter layer definition,
identifyParams.layerDefinitions[3] = "DateOn <= '" + ondate + "' AND DateOff >= '" + offdate + "'";
I get an error
"0x800a138f - JavaScript runtime error: Unable to set property '3' of undefined or null reference"
So, I found on another post to try setting the layer definition like this:
identifyParams.layerDefinitions = { "3": "DateOn <= '" + ondate + "' AND DateOff >= '" + offdate + "'" };
I do not get an error, but the identify layer definition is not getting set.