title: Partition Kinesis firehose S3 records by event time
body: <p>Firehose->S3 uses the current date as a prefix for creating keys in S3. So this partitions the data by the time the record is written. My firehose stream contains events which have a specific event time. </p>
  
  <p>Is there a way to create S3 keys containing this event time instead? Processing tools downstream depend on each event being in an "hour-folder" related to when it actually happened. Or would that have to be an additional processing step after Firehose is done?</p>
  
  <p>The event time could be in the partition key or I could use a Lambda function to parse it from the record.</p>