I want to schedule a report for the last day of every month. While scheduling a report I have the option to select the Schedule Type and Next Run Time. If I schedule a report to run every month and define the next run time as 31st January, 2012 it will for sure run on that date but what happens in the month on February (with 28 days) or April (with 30 days)?

If a report is scheduled to run on 31st January, 2012 in the subsequent months with total days less than 31, it will run on the last day of the month.
So the schedule will run as below:
January – 31st
February – 29th
March – 31st
April – 30th and so on..