In the aws-step function [documentation](http://docs.aws.amazon.com/step-functions/latest/dg/amazon-states-language-choice-state.html#amazon-states-language-choice-state-rules), it seems possible to write a 'choice' state comparing variables from the current state. However, is it possible to write a timestamp comparison referencing the current time? For example, say I want a particular state to be enabled when the time in my state's `$.myTime` property is `TimestampGreaterThan` the `[current time]`. For example:

```
{
   "Variable": "$.myTime",
   "TimestampGreaterThan": "<the current time>",
   "Next": "MyTimeSpecificState"
}

```

Is it possible to reference the current time, or do I have to manually set that on the state in a separate task?