Hey guys!

Hey babe, import the file as a list of pairs {{tString, vReal}, ...} then augment each pair using a function like

In[61]:= Clear[freistadtTime]
freistadtTime[s_String] :=  ToExpression[StringSplit[s, ":"]].{3600, 60, 1}

In[63]:= freistadtTime["10:51:24.708"]
Out[63]= 39084.7

making each pair into a triple {t,v} goes into {t, freistadtTime[t],v}.

Now plot from the new list the Rest of each triple, but use the First of each triple to label the graphics.

If the time interval goes over midnight, one has to take that into account. If more hints are needed, please deliver a sample data file.