How to calculate difference between two dates and use as grouping

[sszretter]

 In JasperReports (iReport), how can I take a date field from the database and calculate the difference between that and the current date (for example to calculate age) and then GROUP the report on that value (age 18 group, age 19 group/break, etc.)?

date field in iReport:

$F{dob}
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example of how I calculate the age - at least to display it on the report, but I want to break on this value somehow:

<![CDATA[theDate=new Date($F{dob});  currentDate=new Date(); Math.round((currentDate.getTime()-theDate.getTime())/1000/60/60/24/356)]]>
[/code]

Thanks!