I found this on an American dictionary site: "By definition, 12 a.m. denotes midnight, and 12 p.m. denotes noon, but there is sufficient confusion over the meanings of a.m. and p.m. when the hour is 12 to make it advisable to use 12 noon and 12 midnight where clarity is required."

Fowler's, however says

"According to standards bodies such as the National Institute of Standards and Technology in the United States, noon is neither AM nor PM, because noon is neither before nor after itself. Following this logic, 12:00 AM is the midnight at the start of the day (the only 12:00 that is before noon), while 12:00 PM is the midnight at the end of the day (the only 12:00 that is after noon).

However, it is common practice in the US to interpret 12:00 PM as noon, because 12:01 PM through 12:59 PM come immediately afterwards. Even 12:00:01 PM is unambiguously one second after noon, nowhere near midnight. By either convention, 12:00 AM is the midnight at the start of the day. But even this can be confusing, because one hour after 11:00 AM is noon, not midnight.

As a result of these conflicts, many people, even many of those who use the 12-hour clock regularly, can be confused about what times "12:00 AM" and "12:00 PM" refer to. Therefore it is often clearest to simply write "noon" or "12:00 noon" for noon. But midnight remains problematic, because simply "midnight" or "12:00 midnight" could mean either the midnight at the start of the day or the midnight at the end."

Clear as mud. And I still don't know when they were going to do the work.

Amusing to see the faces in the times I wrote with "xx" seconds after the hour - - forgot (or never knew that"colon, followed by the letter x" produces this icon.

Thus, I was trying to say "1 7 : x x", "7 : x x", and so on...