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A great library for graphs is this one:https://github.com/danielgindi/Charts

That seems to work. I'm new to Persistent History Tracking and I thought changedObjectID is just the ID which is irelevant after the object has been deleted.Thanks a lot

You can definitely use core data. But I'd run some performace tests before deciding. Create a UNIT test which will simulate one year worth of data and try to draw a graph. My guess is that you will need to implement some summarization - like another entity which will represent one day's data summary. How exactly this can work depends on your data model.I did something simmilar for my app. I have to say core data performance on iPhone surprised me in a positive way.