HOW TO CREATE AGING PERIOD DEFINITIONS IN DYNAMICS 365?

You can use aging period definitions to analyze the maturity of customer accounts and vendor accounts, based on a date that you enter.

Note:: all reports in Dynamics 365 for six periods only, if you need more, you must make some customization 

Click Accounts receivable > Setup > Collections > Aging period definitions.

click new to assign code and description for the period 

click add below to add your periods, and you can organize it by up and down button 

you have multiple selections in the interval as the below 

Ledger period / The interval is the length of the period that is defined for the fiscal calendar    that is selected in the ledger form

or select interval by day/week /month/quarter/ years/unlimited

Note:: you can print aging in reports from top row period or down row period based on 

Printing direction 

Forward – Print columns in the same order in which the headings appear in the table, starting with the top row.

Backward – Print columns in the reverse order in which the headings appear in the table, starting with the bottom row.

also, you can navigate the aging period definition from 

Accounts payable > Setup >  Aging period definitions.

Now, you can print aging reports as the below 

select your criteria, you can see more details here 

don't forget to filter vendors that you need 

also, you can print customer aging as the same

you can print aging in customer account statement (external)

for more information about aging periods, check this link