rrdtool create node-1.rrd --start `date +%s` --step=300 \
DS:getattr:COUNTER:600:0:U \
DS:access:COUNTER:600:0:U \
DS:read:COUNTER:600:0:U \
DS:write:COUNTER:600:0:U \
RRA:AVERAGE:0.5:1:2016 \
RRA:AVERAGE:0.5:288:31 \
RRA:AVERAGE:0.5:2016:52


RRA1: 604800
RRA2: 2678400
RRA3: 31449600 
---------------
      34732800 seconds = 402 days.

So, theoretically I should be able to get the oldest data point by taking `date +%s` - 34732800.

But, that seems not to be the case, as demonstrated here:

server~$ echo "`date +%s` - 34732800" | bc;
1140373981

server~$ rrdtool fetch node-1.rrd AVERAGE --start $(echo "`date +%s` - 34732800" | bc) | head -3; rrdtool fetch node-1.rrd AVERAGE | tail -1
timestamp    getattr           access            read              write

1140048000:  nan  nan  nan  nan
1175106900:  nan  nan  nan  nan



The number returned by the first command ought to match the first number in the fetch, but it does not?