In what context do you want to display the dates? Is it in a filter pane, chart or table?
Generally I would suggest adding a flag in your data model to identify the rows related to the desired time period. For example in this case it could be inline with;
If(MyDate = Today()-1 OR MyDate = Today(), 1, 0) AS MyDateTodayOrYesterday
In your visualizations you can then use a set expression to target aggregations to the flagged rows.
For displaying the same dates as one value you can concatenate the values
Without the flag in data model the set expression would be