If i graduated high school in 2007 when did i start

If you graduated from high school in 2007, you started high school in 2003, assuming you studied high school in the US.

Explanation:

High school lasts 4 years in the USA, so we can say that if you graduated from high school in 2007, you started it in 2003. In high school, the choice of subjects is much more flexible; The student has to take the 4 compulsory subjects: English, math, history and politics. The other subjects: physics, chemistry, arts, writing, debate, sports, cooking and others, are optional, that is, the student chooses those who have preference to attend.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.