Group Valid Event Dates by Month
Count valid event dates by YYYY-MM and return a dictionary of month counts. Each valid date must be an exact ASCII YYYY-MM-DD string representing a real Gregorian date. Use datetime parsing; skip invalid dates, non-string entries and other formats. Count duplicates as separate events.
Difficulty: intermediate
Examples
[["2024-02-01","2024-02-29","2024-03-01"]]{"2024-02":2,"2024-03":1}