Date Difference Calculation in OBIEE 11g

For Date Difference........

TimestampDiff(interval, timestamp1, timestamp2)

ex:TimestampDiff(SQL_TSI_DAY, cast('1-apr-2011' as date), current_date)

Where:
interval
The specified interval. Valid values are: SQL_TSI_SECOND, SQL_TSI_MINUTE, SQL_TSI_HOUR, SQL_TSI_DAY,
SQL_TSI_WEEK, SQL_TSI_MONTH, SQL_TSI_QUARTER, SQL_TSI_YEAR.