how to use PERIODSTODATE in BPC 10 NW member formula

Hello Experts,

Can you please help  me to understand  how to use PERIODSTODATE  in BPC 10 NW member formula.

Below syntax are not working, it just retrieving current period balance not added  all previous periods balances.

SUM(PERIODSTODATE([TIME].CURRENTMEMBER),[ACCOUNT_HR].[HC_HR_FTE]) – retrieving  only current month balance

SUM(PERIODSTODATE(YEAR,[TIME].CURRENTMEMBER), ),[ACCOUNT_HR] .[HC_HR_FTE]) – “YEAR” not accepted. Giving error. 

Thanks in advance

Regards

Pavan