How is the day number represented in the "Date of Latest Revision"?

The correct representation of the day number in the "Date of Latest Revision" is based on the last three digits of the code. In aviation publications and charts, the format typically employed includes the year followed by a sequential number representing the day of the year. The day number, therefore, is denoted by these last three digits which count sequentially from 001 to 365 (or 366 in a leap year), effectively indicating the specific day when the document was last revised.

This method is particularly useful for pilots and aviation professionals, as it provides a clear and concise way to ascertain the currency of the charts or documents without ambiguity. The sequential nature of this numbering system allows for easy tracking of revisions over time.

Other options do not correctly describe how the day number is represented. For instance, a universal calendar suggests an external reference system rather than the straightforward sequential method used in aviation documents. The notion of using a custom software for yearly counts does not apply, as the representation is standardized and not reliant on specific software to interpret the day number.