 At the start of a new month, the items for that month are removed from the month folder and placed in the corresponding daily folders.Simple systems which involve many repetitive tasks over time tend to use and re-use index cards of an appropriate size, with more complex systems using expandable "accordion files", file folders or even entire rooms full of filing cabinets.Modern systems are usually maintained in computerized databases or with simple tools such as a Unix ".calendar" file, a Microsoft Outlook calendar, etc.