Final answer:
The TO_DATE function is used in Oracle12c to convert a string to the standard date format for internal storage and operations.
Step-by-step explanation:
The function that allows a user to enter a date in a variety of formats, and then changes the value to the default Oracle12c internal storage format is TO_DATE. This function is commonly used in SQL queries to convert string data to a date format that Oracle can understand for date-related operations. It's important to use the correct syntax to ensure the date is interpreted correctly.