Leap year bugs typically fall into two categories, based on the amount of impact they may have in real-world usage:[1] The following Python code is an example of a Category 1 leap year bug.
The date constructor will raise a ValueError with the message "day is out of range for month".
Then, it will modify st to represent February 29 of a common year, a date which does not actually exist.
Passing st to any function that accepts a SYSTEMTIME struct as a parameter will likely fail.
Since that return value is unchecked (which is extremely common), this will result in ft being left uninitialized.