bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic MyTopic --config retention.ms=1000
... wait a minute ...
bin/kafka-topics.sh --zookeeper localhost:2181 --alter --topic MyTopic --delete-config retention.ms
bin/kafka-run-class.sh kafka.tools.GetOffsetShell --broker-list kafkasrv:9092 --topic mytopic --time -2
bin/kafka-run-class.sh kafka.tools.GetOffsetShell --broker-list kafkasrv:9092 --topic mytopic --time -1