There is no hard and fast rule and some lenders are more flexible than others, or too busy to repo the car at the moment the payment is one day late.
However, the lender's rights, and yours, are spelled out in the note that you signed at the time that you signed the documents for the car loan. So, you can go back and read it. Or, take my guesstimate that since they wrote it, that technically, the day that the payment was late, the loan was in "default" and that invoked all of the lender's rights, including the right to repossess the car at that time.
This answer is provided for informational purposes only. Actual legal advice can only be provided in an office consultation by an attorney licensed in your jurisdiction, with experience in the area of law in which your concern lies.