First, you would need @sys.date
entity if you want to catch value of entities like tomorrow
instead of @sys.time
Now coming to the question, directly extracting the parameter value will only give us parsed date value, not the original value.
But if we set an output context, then from that context we can extract both parsed value and the original value as intended.
Here is a request that we get on webhook we can get date and date.original by parsing the output-context that we set in the intent:
{"responseId":"###","queryResult":{"queryText":"are you open
tomorrow","parameters":{"date":"2018-12-28T12:00:00+05:30"},"allRequiredParamsPresent":true,"fulfillmentText":"","fulfillmentMessages":[{"text":{"text":[""]}}],"outputContexts":[{"name":"projects/###/agent/sessions/###/contexts/time","lifespanCount":5,"parameters":{"date":"2018-12-28T12:00:00+05:30","date.original":"tomorrow"}}],"intent":{"name":"projects/###/agent/intents/###","displayName":"time-intent"},"intentDetectionConfidence":1,"languageCode":"en"}}
