One customer recently asked for a mode of operation more like WWV than the USNO. That is, 59 ticks and one beep per minute, with a single time announcement in the last ten seconds. 

To accommodate that, there is now a WWV macro in the firmware, so this mode is a compile-time choice.

I’ve also been asked to make a 12 hour AM/PM clock.

You can actually do that by just re-recording the hour audio samples. You can do that by just copying the 12 sample over the 0 and copying 1 through 11 over 13 through 23. That would give you a purely 12 hour clock. If you want AM/PM as well, then you have to either re-record all the hour files to add AM or PM... which would result in a script like “At the tone, Pacific Daylight Time will be 4 PM, 23 minutes, 10 seconds.” If you’d prefer “4 hours, 23 minutes, 10 seconds PM,” then firmware work would need to be done to support it.

Frankly, I like the easy way, and not just because I’m lazy. It just seems a more natural way of reading it.