We have cases in which there is no date in the log files, meaning, only the time of the event is in the data. What can we do in such cases?
If you are indexing the files as they are written (as opposed to batch or historic imports) Splunk will 'assume' that the date is "today"(actually, it will assume the date is the same as the log modification date or the date on which is its indexed)
This can be problematic in the few seconds around midnight, so it is not ideal.
Unless there is some other field you can get the date from (maybe the filename eg 01012020.log) Then realistically your options are:
Fix the app/logs
Accept midnight glitches
If you look at a historic log line, is there anyway to figure out what date it was generated?
Do the filenames contain dates?
Are these in Splunk logs or a specific application? I am assuming you will need to address the issue with the specific application's logging functionality to ensure full timestamps are being recorded that include time AND date of events.