query on ILR SETO application

hi all,
I will be applying to HSMP early next year, i am going through the SET O application and found this

When did you (the main applicant) first enter the UK? This refers to the date of your first entry into the UK at the beginning of the period of stay on which this application is based.

I first came to UK in on working holiday visa and then changed my status to HSMP and then to tier1 general

My query is....do i need to give the date of my entry with working holiday visa or date of stamping on HSMP visa
i applied for HSMP incountry and was issued ,

Please help me with your expert advice
Many Thanks

date on which HSMP was stamped in passport.