can you reproduce that in apex.oracle.com
Supplying your query would also help. And a screenshot.
...as would a definition of "mangled". It appears that you're trying to use a time based X-axis. Assuming that the values actually returned by your query are date values, you'll need to set the Time Axis Type to either Enabled, Mixed Freq, or Skip Gaps (Automatic doesn't seem to cut it). Then you can use the Format Type and Pattern fields to control how the values on the X-axis look. Note that when using custom patterns, you do NOT use the familiar Oracle date/time format strings - that value needs something else. Google "CLDR date time formats" for details.