> at = Attack.find_by_sql(\
>   "SELECT MIN(occured_on) " +\
>   "FROM attacks " +\
>   "WHERE occured_on BETWEEN '#{start_date_str}' AND 
> '#{end_date_str}'")[0].min

Try using Attact.connection.select_one("SELECT MIN(occured_on)...")

That should return the value without needing to do [0].min. I'm 
actually not quite sure why it works on your machine. I would have 
thought you needed to do "MIN(occured_on) as min" to get the effect 
you're looking for.

But in any case, you should grab the connection like my example above. 
It's a slight misuse of AR to load real objects just to get one 
aggregated value.
--
David Heinemeier Hansson,
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