Following my discovery of changes made in about macOS 11.2, I am now working through my apps bringing their access to time in line with its new behaviour, so that you should be able to run them regardless of your clock settings. Even if your Mac uses a Buddhist calendar, a 12-hour clock and is set to summer time in Mongolia, dates and times should now appear correctly.
This new version tackles this in two ways. During its opening checks, it establishes whether macOS can return time values in the format which it needs. If it can’t, because of further changes in Big Sur, it will prompt you to switch to a 24-clock. That should never happen.
Once it has confirmed that time values are generated correctly, all its dates and times should appear consistently, even those shown in the headers of its reports. If you come across any anomaly or error, please let me know as soon as you can.
My next app to undergo thorough rewriting in this way will be Ulbow.