To calculate the age between two dates in an OBIEE report, use the TimestampDiff function to get the number of days between the from and to date columns. TimestampDiff returns the number of days between the dates, accounting for the fact that OBIEE uses timestamps by default rather than just dates. You can calculate the number of days between two specified dates or between a from date and the current date.

1. To Get Column for Age between two Days in OBIEE Report
For Getting Age between two dates we use SQL Query as :
DATEDIFF ( d, startdate , enddate ) as Age
However default date format in OBIEE is Timestamp. So you need timestamp
function ( Available under Calendar/Date Function Heading.
For Number of Days between two days:
TimestampDiff(SQL_TSI_DAY, “FROM_DATE_COLUMN”, “TO_DATE_COLUMN”)
For Number of Days till current date:
TimestampDiff(SQL_TSI_DAY, “FROM_DATE_COLUMN”, CURRENT_DATE)