Work out what number day of the year it is.
toDayOfYear([1, 1, 2000]) => 1
The argument passed into the function is an array with the format [D, M, YYYY],
e.g. [1, 2, 2000] for February 1st, 2000 or [22, 12, 1999] for December 22nd, 1999.
Don't forget to check for whether it's a leap year! Three criteria must be taken into account to identify leap years:
- The year can be evenly divided by 4;
- If the year can be evenly divided by 100, it is NOT a leap year, unless;
- The year is also evenly divisible by 400. Then it is a leap year.