I am guessing that your reports have some date range, maybe defaulting to jan 1 of this yr until today--or perhaps better yet, would be just the year desired.

if so, then what you need to do is to change this date range in your code. Since jan1-march31 of this year is part of LAST fiscal yr, you would want to exclude them...and the converse when you are in jan1-march31 of a year you want to include apr1-dec31, as well as the jan1-date. So...

I would think that a formula (or an addition to the record selection criteria) would be something like this, assuming you are inputting a year desired (fiscal would be nice ;) )

if YEAR({table.field}) = {?fiscalYear} AND MONTH({table.field}) >= 4 then
true //include the record...apr or later
ELSE
if YEAR({table.field}) = {?fiscalYear} + 1 AND MONTH({table.field}) < 4 then
    true //include...first 3 months of prior year
else
    false //not in the months you are looking for.

This is premised on the fiscal year being the year that you are starting...fiscal 2013 is apr2013 - march2014...otherwise you will some slight tweaking of signs.

HTH

hmm...
that makes it a bit more difficult, but not much...well maybe.

If the data was being retrieved via a stored proc, it would be simple to add a column that would be the fiscal year, and then you could just group on that.

without a stored proc, we just have to create a formula that mimics the determination of the fiscal year for the event date...
local numbervar fiscalyr := year({table.eventDate}); // not a bad default, most of the months are fiscal year
if month({table.eventDate}) < 4 then //jan/feb/mar
fiscalyr := fiscalyr - 1; //in the prior yr
fiscalyr //displays the fiscal yr

now that we have the formula, we can use it to group the data, and presumably the graph...I haven't used graphs, as the reports have been all numbers.

HTH