Thanks for taking the time to reach out to the QuickBooks Community. I'm here to help provide some insights about the budget feature in QuickBooks Online (QBO).
The program's budgets operate based on your fiscal year so that you can plan and monitor the numbers during that time frame. Currently, there isn't an option to change the period date in a budget. It's our priority to provide products and services that suit your business needs, and I'll make sure to take note of this.
In the meantime, I'd suggest visiting our QuickBooks Online Blog regularly. This way you'll be updated with the latest news and updates including product improvements.