I’m only iterating over the dimension Date table, so not immediately…
There have been a couple of threads on performance, here’s a link to one but use the search option to find others. @Nick_M has shared some great content on that subject.
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If you have multiple date fields in a single fact table BUT they need to be treated equally in your DAX calc you basically have 2 options; no relationship or all inactive relationships.
However your report could include other Measures for which filtering does need to take place on a single date field from that fact table then you can use TREATAS / USERELATIONSHIP depending on what choice you’ve made. Here’s a video explaining TREATAS
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I hope this is helpful