I want to try advertising for 1 day to see what the results are. It seems that my campaign budget has to be for at least a month though. How do I register a budget for only 1 day? Is this possible?
You can't budget for one day, but you can work out what daily budget you want, set your monthly budget to reflect that, then set a start and end date so that it only runs for one day. Or alternatively, just pause it after one day.
just keep in mind that one day is a very short time to fully test adwords. I would suggest you use a small budget for longer period.