In this case, "to be" is used twice because the question is asking for two separate pieces of information: "What is today's date?" and "What is today's date?". Each instance of "to be" is used to link the subject ("Today") with the predicate ("date") to provide a complete statement or question.
Today's date is September 17, 2021.
In this case, "to be" is used twice because the question is asking for two separate pieces of information: "What is today's date?" and "What is today's date?". Each instance of "to be" is used to link the subject ("Today") with the predicate ("date") to provide a complete statement or question.