> Some utility companies bill every 2 or 3 months. This makes monthly stats meaningless (why is September so high compared to August? did I spent too much or is it the effect of the phone bill of the previous quarter?).

According to Claude 3.5, ledger/hledger handles that situation like this:

    ; Automatically allocate $60 quarterly phone bill across 3 months
    ~ monthly
      Expenses:Phone          $20
      Liabilities:Accrued    $-20
    
    ; When actual bill comes
    2023-09-15 Phone Company
      Liabilities:Accrued     $60
      Assets:Bank            $-60

This approach:

1. Accrues monthly portions ($20) to a liability account

2. When the real bill arrives, clears the accrued amount