Prints date spans.
$ days # Prints current month
$ days +6 # Prints span now plus 6 days
$ days -3 # Prints span now minus 3 days
$ days 2025-08-02 # Prints span 2025-02-02 - now
$ days 2025-08-02 +6 # Prints span 2025-08-02 plus 6 days
$ days 2025-08-02 -3 # Prints span 2025-08-02 minus 3 days
$ days 2025-08-02 2025-09-20 # Prints span 2025-08-02 - 2025-09-20
$ go install github.com/jsageryd/days@latest