Well, I had no idea of what I was doing, but that has never held me back.
I believe I mentioned that I found the "17h 12" entry in a data file named level12. It was a dumb idea, but I thought I would try to fix it in a text editor but of course that did not work.
But then I saw someplace that this type of file is called a binary file. So, it stood to reason that there would be a binary editor, yes? Free, hopefully? And sure enough, I found one at SourceForge:
https://sourceforge.net/projects/wxhexeditor/
Now of course, when I opened the level12 file in this program, it looked like gibberish to me. Yet it had a search function ...

- Image 2 - before.jpg (604.74 KiB) Viewed 595 times
... and I figured out that you edit on the right, not the left (I guess, but it worked); so I inserted six spaces in place of "17h 12" as follows:

- Image 3 - after.jpg (613.94 KiB) Viewed 595 times
The key, of course, is the ability of the binary editor to save the altered file in the proper format, which apparently was successful. When I started OOB and looked at a Mission Overview, "The current time is 5:12 PM" (17h 12) phrase was gone!
So, I will offer the altered file in the zip attachment below. Caveat emptor, of course. Or, said another way, YMMV. In Windows and with a Steam installation, the level12 file is located here:
C:\Program Files (x86)\Steam\steamapps\common\Order of Battle Pacific\Order of Battle - WW2_Data
The downloaded version of the game would have a similar data folder. That one, however, would be under C:\Program Files\Slitherine\Order of Battle if memory serves.
You may need to be logged on as administrator to substitute this altered level12 file for the original one. Common sense says to back up the original level12 file first and have the game turned off when you do this. If it fails, bring the original file back to the same location. Hopefully, though, if you choose to use this file, it will also work for you. Good luck!