"Net 30" and "due in 30 days" are typical trading terms that are usually set by the supplier and agreed to by the account customer prior to them purchasing goods/services.
This means that the account customer needs only pay 97.5% of their account debt if they pay it on or before the payment period end date.
If the trading terms do not include a payment incentive discount, then the trading terms will be described as "Net 30" i.e.
This allows the company a few weeks to pay for the goods. In this case, the invoice is due within 30 days after receiving it, but 30 days doesn't always fall on the end of a month.
When the credit terms list EOM, usually the debtor has until the end of the month in which it is due to pay the bill.
As long as they are not paid, your bills' value goes down because of inflation.