What's best: If statement VS Calculations and operators

In my little coding experience, I have always wondered what was best practice: using if statements and loops, which I find is a lot easier for me to write/read; or achieving the same result using a single (or a few) calculation with some logical operators, which for me takes a lot more thinking and time before coming up with the correct calculation.

Here's an example... Say you want to convert the year (ex. 2019) in days since 01/01/0001, which would be 737059 days according to this matlab code:

>> datenum(datetime(2019,1,1)-datetime(1,1,1))
     737059

You of course have to take into account leap years. The first way to do this would be with a loop and if statements, so something like (in pseudocode):

days = 0
for y = 1 to 2018
  if (y not divisible by 4)
    days = days + 365
  elseif (y not divisible by 100)
    days = days + 366
  elseif (y not divisible by 400)
    days = days + 365
  else
    days = days + 366
  end
end

The other way to do it is with some math and some operators (in MATLAB):

days = (2019-1)*365 + floor((2019-1)/4) - floor((2019-1)/100) + floor((2019-1)/400)

Both alternatives give the same result, but which way do you think would be the "best" way to write code? In which circumstance would one be better than the other?