Have you configured your system to use Text-to-Speech until now or it’s the beggining?
You can see one example here: HowTo: Listen & Talk to your Home (follow only the Google TTS part of the turorial)
for the format of the say command to compose the Date & Time string to be send as Text to the TTS engine: check the forum for examples. I believe that there are many. You can also look for logInfo statement examples to see how to format this.