Given a string `date` representing a Gregorian calendar date formatted as `YYYY-MM-DD`, return the day number of the year.

Example 1:

    Input: date = "2019-01-09"
    Output: 9
    Explanation: Given date is the 9th day of the year in 2019.

Example 2:

    Input: date = "2019-02-10"
    Output: 41

Constraints:

- `date.length == 10`
- `date[4] == date[7] == '-'`, and all other `date[i]`'s are digits
- `date` represents a calendar date between Jan 1st, 1900 and Dec 31th, 2019.