TCODE - PPOME

Hi Frineds

Can any one tell me what is "Assigned as of" and "Assigned untill" dates in PPOME TCODE screen

Here i have faced a problem, i have assigned a person to position from 23.07.2008 and "Assigned as of" also the same date i have given instead of 27.01.1980 (my org unit start date)

and remaing all positions are with 2 types of dates in this columns - actual position date and "Assigned as of date - as 27.01.1980

how could i change the date in "Assigned as of " column in PPOME screen, plz help me. need to change it

immediate

Thanks

Lakshmi