Today I was using our Historian server and wanted to get the first (and maybe last) data point in history. The spec part 11 v 1.04 says:

"A.2 Determining the first historical data point

[...] one of the following queries using ReadRawModifiedDetails parameters:
returnBounds=false
numValuesPerNode=1
startTime=DateTime.MinValue+1 second
endTime= DateTime.MinValue
Or:
returnBounds=false
numValuesPerNode=1
startTime=DateTime.MinValue
endTime= DateTime.MaxValue"

The first method returns the first data point while the second method actually returns the last value.

I was blaming the developer of the server but he reponses with "6.4.3.2 Read raw functionality

If [...] endTime and numValuesPerNode alone are specified then the data will be returned in reverse order."

That means: if start time is not sepcified (= DateTime.MinValue in second method) then the reverse order comes into play. Together with numValuesPerNode = 1 it will return the last value in history.