Which is date of first successful Tier 1 application?

[kannit]

Hi,

I am trying to check my score on Points Based Calculator but I am not sure of answer to one question:

Date of your first successful Tier 1 application?

Here is my situation:
1) Applied via post for HSMP approval on 25-NOV-2007
2) Approval received in Dec-2007 (date not sure)
3)Applied for Tier 1 (General) visa using HSMP approval in March or Apr-2008 as the system changed from HSMP to Tier 1 in meantime.
4) Received visa with start date 14-Apr-2008

Which date should I use - (1) , (3) or (4) ?

Thanks!