>>>Closest UP or Closest DOWN?
>>>What if you have:
>>>

>>>456   04-28-2009	Low
>>>456   04-25-2009	Zero
>>>456   05-10-2009	Something
>>>

>>>What record should be chosen?
>>
>>My assumption was that we need the lowest time difference. Otherwise the problem is trivial.
>>
>>But actually, even in this case it is still trivial if we get the time difference in the result.
>
>And if the time diff is equal? Which one?

Good point - I don't know.