In the Exchange Management Shell, to get a list of mailboxes by creation date in ascending order:
Get-Mailbox -ResultSize unlimited | Sort-Object WhenMailboxCreated | ft Name,WhenMailboxCreated -autosize
To get a list of mailboxes by creation date in descending order:
Get-Mailbox -ResultSize unlimited | Sort-Object WhenMailboxCreated -descending | ft Name,WhenMailboxCreated -autosize
To get a list of mailboxes created in the last 30 days in descending order:
Get-Mailbox -ResultSize unlimited | Where {$_.WhenMailboxCreated -gt (get-date).adddays(-30)} | Sort-Object WhenMailboxCreated -descending | ft Name,WhenMailboxCreated -autosize