This is more of a speculation, but I have tried opening a log file around 1 AM (UTC +1) and getting an error telling me the file data/logs/2014/10-October/20-Monday.log does not exist. As it just turned 20th of october one hour ago, it's not impossible that the client feeds client-side time in these cases instead of server-side time. Again, speculation. I haven't even tried to open a daily log file any other time, so yah.
This is more of a speculation, but I have tried opening a log file around 1 AM (UTC +1) and getting an error telling me the file data/logs/2014/10-October/20-Monday.log does not exist. As it just turned 20th of october one hour ago, it's not impossible that the client feeds client-side time in these cases instead of server-side time. Again, speculation. I haven't even tried to open a daily log file any other time, so yah.