Date sorting doesn't work with single digit month/day

[JesseFL]

4/8         Opening Balance
    Assets:Checking                     $10
    Equity:Balances                     $-10

4/9         Paycheck
    Assets:Checking                    $100.00
    Income:Boss
    [Equity:Budget]                     $-100
    [Budget:A]                          $70
    [Budget:Z]                          $30
    
4/12        Groceries
    Assets:Checking                   $-10.00
    Expenses:Groceries
    (Budget:A)                        $-10

4/4   test
  test    $100
  test2   $-100
  
4/5   test2
  test    $100
  test2
  
4/7   test3
  test    $100
  test2
  
4/10    test4
  test    $100
  test2
  
4/2   test5
  test    $100
  test2