Calendar.parse_naive_datetime

You're seeing just the callback parse_naive_datetime, go back to Calendar module for more information.
Link to this callback

parse_naive_datetime(arg1)

View Source (since 1.10.0)

Specs

parse_naive_datetime(String.t()) ::
  {:ok, {year(), month(), day(), hour(), minute(), second(), microsecond()}}
  | {:error, atom()}

Parses the string representation for a naive datetime returned by naive_datetime_to_string/7 into a naive-datetime-tuple.

The given string may contain a timezone offset but it is ignored.