Deductions & credits

Assume it's >50% biz use and tax year biz profit is significantly more than cost of vehicle and of course that profit is at it's max at the end of the tax year.  Are you implying that the income used for reference can span more than one tax year for a schedule 179 deduction?  I thought the gist of this deduction was that it allowed you take the majority of the cost of the vehicle in the first year of ownership (service) as opposed to depreciating over multiple years.  The essence of my question has to do with the timing of the purchase and placed in service date.  As I said, just playing around with different placed in service dates, there's a signficant difference between using a 1/1/2020 and for instance anything more recent than 7/1/20.   So, I'm trying to determine if it makes more sense to buy the vehicle next year and take the full deduction then which I assume is based my income for that year.