Epmmemberoffset issue with TIME Dimension PARENTH2

Hi

I have a second hierarchy in the Time dimension to calculate a rolling total for forecast time base members which may be different from the calendar time totals, example PARENTH2 total for current forecast total can be 2014.FEB to 2014.FEB.

My current forecast total is for months 2014.JAN to 2014.DEC, I'm using ="epmmemberoffset(,2014.DEC,1)" and expect to get 2015.JAN in the cell but I'm getting 2014.JAN

Any ideas on what the issue is?

Thanks

William