On the last day of each month, the Z1 Auto only ‘logs’ the time used between the start of usage and midnight. It does not report any time between midnight, and morning of the first morning of the month. Is there a fix to this problem?

Your viewing window may be set incorrectly. In order to fix this, go into chart settings by using the gear button in the top right corner of the main Nitelog screen. Change your usual sleep time to the time you went to sleep and change the hours of sleep to 12. You should now be able to view your data for the night selected.