[rrd-users] Biased graph - shifted average periods

[Igor I. Shulz]

Help pls
My brain is boiling out.

I've created rrd-file to accumulate data on a per-hour-basis (--step 3600). Thre are two AVERAGE sets:
RRA:AVERAGE:0.5:4:62
RRA:AVERAGE:0.5:24:45

--start set on the edge of a day - 1242248400

But 4-hour averages are not set on even 4-hour ranges (00:00, 04:00, 08:00 etc), but are set on ranges 03:00, 07:00, 11:00. This is part of dump of my rrd-file:

                <cf> AVERAGE </cf>
                <pdp_per_row> 4 </pdp_per_row> <!-- 14400 seconds -->
                <xff> 5.0000000000e-01 </xff>
...
                <database>
                        <!-- 2009-05-03 19:00:00 EEST / 1241366400 --> <row><v> NaN .........
                        <!-- 2009-05-03 23:00:00 EEST / 1241380800 --> <row><v> NaN .........
                        <!-- 2009-05-04 03:00:00 EEST / 1241395200 --> <row><v> NaN .........
                        <!-- 2009-05-04 07:00:00 EEST / 1241409600 --> <row><v> NaN .........

Daily average (by 24 points) is also shifted - periods are not 00:00-23:59, but 03:00-02:59:

                <cf> AVERAGE </cf>
                <pdp_per_row> 24 </pdp_per_row> <!-- 86400 seconds -->
                <xff> 5.0000000000e-01 </xff>
............
                <database>
                        <!-- 2009-03-30 03:00:00 EEST / 1238371200 --> <row><v> NaN ....
                        <!-- 2009-03-31 03:00:00 EEST / 1238457600 --> <row><v> NaN .... 
                        <!-- 2009-04-01 03:00:00 EEST / 1238544000 --> <row><v> NaN ....

As result I have ugly shifted line on a graphs.

Is it possible to set average periods on the more reasonable points?
00:00, 04:00 ... for 4-hour average
and
00:00, 00:00 ... for daily average