Karte-von-Morgen-API.md

 The backend of Karte von Morgen (KVM) is described [here](https://github.com/kartevonmorgen/openfairdb). It provides an API for accessing items of KVM.
 
+In the API the unix timestamp is used, you can convert it with: https://www.unixtime.de
+
 Find Events:  
 https://kartevonmorgen.org/api/v0/events?bbox=49.8,-1.0,52.5,20.0&start_min=1578182400
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