What is the earliest Start Date that can be applied for a budget?

Question

Hi all,

So I have created a runbook that automatically creates a RG and assigns a budget to it.
I tried to set the budget start date to a variable which calls Get-Date or similar to assign it to the day of creation.
I unfortunately keep getting an error if I do so.
So I just put in 07/01/2021 as the start date and it somehow worked.

So my question is, can this runbook keep running comfortably even if we reach December?
As in the start date for the budget can it be July if the resource group is created in December or does it need to be updated every once in a while or so?

Any help is appreciated. I am very new to Azure