I've always wanted to have wallpapers that change over time. Unfortunately there is no extension in TYPO3 that provides a really good timer. So I programmed an extension myself that does this. But the extension can do even more: It can create appointment calendars and combine appointment periods with each other. A series of appointments like "Every Tuesday from 11 a.m. to 1 p.m., just not during the holidays and public holidays" should no longer be a problem. It says 'should' because the extension is in beta.^{(translated with google 2022-10-31)}