RD or ND for the 6 mont rule

[IP008]

For the date to start counting for the 6 month rule, which date is considered.
Is it
1. the postal date when the 485 application is sent
2. The receipt date
3. Notification date

 

[smarin]

No Title

In my opinion it should be ND. But one has to clarify if 180 days means 180 calendar days and not 180 working days.