I'm new to Splunk and have what I think is a strange use case (maybe not!). We are capturing logs from an embedded device without a battery powered clock and therefore when booted the device has no reference to the current time. It generates logs from a time of 0 and timestamps the log events with a time offset in . e.g. 9.307.
The device does generally get a time reference quite soon after boot from NTP (if network connected) in the log, so I could pre-process the logs, parse out the time and write a valid timestamp for each event by recalculating the offset.
In this case, I would probably use DATETIME_CONFIG=CURRENT and just let the indexed time of the event be close enough... I am assuming you are forwarding these over the network, and they will arrive at the indexer within a few milliseconds of being created on the embedded device. If not, this will not work.