Why is there :nopm: in some photo file names? I was looking at some of the pictures taken with my camera (Google Camera) and there are some that have :nopm: in the file name. The format of the file names are the same, just some contain this after the timestamp, before the extension.



When I use MTP on windows to copy them to my PC they copy fine, because it removes the : from the file name. 

What is the meaning of the :nopm:?

I have added a more detailed picture that shows :nopm: does not have anything to do with if it was taken in the morning. This wouldn't make sense anyhow, as the timestamp is already in 24 hour format. 231314 = 11:13PM, there is no need for an AM/PM indicator.
This is not related to AM/PM as the screenshot shows. This issue appears to happen due to Google Hangouts. I have heard from a few Moto G owners that this happens a lot on that device, and can cause issues moving to SD card, however, it really seems to be down to Google Hangouts. 
Here is a mention on Reddit, and on an unrelated thread the same issue crops up. 

Upon reading this issue on Github: 


  google hangouts produce [sic]images of this form image_timestamp.:nopm:.png


There is no easy fix at present, but I will investigate.