180 days count start date?

[ChinnaKmm]

What is the date for 180days count start, is that RD or ND. My RD and PD are about 4months apart?

Any input is appreciated

 

[eeshwar]

It is RD: Receipt Date

 

[ginnu]

ChinnaKmm:
If I-485 is filed based on approved I-140 then the date of filing or RD
If it is concurrent filing then read:
http://www.murthy.com/UDportis.html