Age of Qurbaani Animals

Calculating the age of an animal for qurbaani according to the Islamic date

Q: We slaughter goats for Qurbaani. We understand that a goat needs to be one year old. Must it be an Islamic year, or English?

The farmer gave us the date of the birth of this goat, and it was born on the same date as Eid (Islamic date), exactly a year ago. So it's exactly 1 year old, must we still check if it was born in the morning or afternoon, to make make sure we dont slaughter it before time?

Slaughtering cattle under 2 years

Q: I do qurbani on behalf of people. lately I found out that the criterion for cattle was minimum 2 years. In the past I slaughtered  a grade cattle which are generally under 2 years. This was done totally unintentional. It was not done to save money as a grade are the most expensive. What is the ruling for the past qurbani as it is difficult to remember how many were made and whether it was nafl or waajib?