Modify Availability for outages

We have NPM 10.5 monitoring approximately 2000 nodes.  We want to provide a monthly report for availability on all WAN devices.  Creating the report is not an issue, however, we do not want scheduled outages to reflect in the totals.  So I basically have two questions:

1. Does NPM still count downtime for availability purposes when the device in placed in maintenance mode?  I've searched thwack for this answer, but I've seen conflicting responses where people say it should not, but tests have shown otherwise.
2. Because our network admins sometimes forget to put the device in maintenance mode is there a way to modify the availability statistics after the fact to reflect the true availability?

Thanks