Using Timestamp

Recently I have come through an business requirement that I have to calculate the number of days from the column 'Document Date' by comparing with current date to find out the ageing period of a customer.
I'm sharing the solution which I have find out using timestamp function in OBIEE BMM Layer.
I hope this may be helpful.
I have created the column called 'DayDiff' in BMM layer with the function timestampiff shown in the below picture:

I have used the same column when we were created the saved request which exactly giving the total number days by comparing two date columns.