The importWorklog method of DefaultJiraDataImporter makes a call to

worklogManager.create(userProvider.getUser(externalWorklog.getAuthor()), worklog, null, false);

The method adds worklog to issue worklog and also adds an item to the history table. The worklog item is ok:

guena logged work - 01/Sep/14 8:01 PM

Time Spent:2 hours
Validate

However, the corresponding history item is not ok:

guena made changes - 8 hours ago

Time Spent 3 hours, 5 minutes [ 11100 ] 5 hours, 5 minutes [ 18300 ]
Worklog Id 11202 [ 11202 ]

It should be like

guena made changes 01/Sep/14 8:01 PM

Time Spent 3 hours, 5 minutes [ 11100 ] 5 hours, 5 minutes [ 18300 ]
Worklog Id 11202 [ 11202 ]