A more thorough explanation:

Definition: On or before is a phrase commonly used in contracts or promissory notes to indicate a specific date by which payment or performance is required. It may also imply that time is of the essence, meaning that failure to meet the deadline could result in serious consequences.

For example, if a contract states that a payment must be made on or before a certain date, the person making the payment must ensure that it is received by that date. If they fail to do so, they may be in breach of the contract and could face legal action.

In the case of Jannetti v. Whelan, the court found that a contractual requirement stating that the contract would be null and void if the closing did not occur on or before a specified date made time of the essence for closing the deal. This means that if the closing did not occur by the specified date, the contract would be considered invalid.

Overall, the phrase "on or before" is used to set clear deadlines and ensure that all parties involved in a contract or agreement understand their obligations and responsibilities.