The problem that I see here is that there is no truly "graphable" data in your output.
You cannot tell Splunk to use a time-scale on the Y axis. At least not for chart or timechart : by definition, the Y axis must be the numeric result of one of the chart or timechart functions, and none of them return time values. max(Time_of_Day) will work only if Time_of_Day is numeric - otherwise it returns null values.
You could do something like this
yoursearchhere
| timechart span=30m count by Database
which will graph the count of events attributable to each database.
You might also look at the xyseries command, but I am not sure that it will do what you want, either...
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