switch? Date table and Table with Date - table with date - handling null values in the table

Hi NeverGiveUp ,

Please update the formula of measure [myCONDITIONS_current_calendar] as below and check if it can return the expected result...

myCONDITIONS_current_calendar =
VAR selected_qtr =
    ISFILTERED ( 'CurrentYearOnlyCalendar'[Quarter Calendar Year] )
VAR selected_fyqtr =
    ISFILTERED ( 'SOSCalendar'[FY Quarter] )
VAR sosdate =
    SELECTEDVALUE ( 'PCMerge'[dsbp_initiative_start_of_shipment] )
RETURN
    IF ( NOT ( ISBLANK ( sosdate ) ) && ( selected_qtr || selected_fyqtr ), 1, 0 )

If the above one can't help you, please provide some raw data in your tables  'CurrentYearOnlyCalendar','PCMerge' and 'SOSCalendar' (exclude sensitive data) with Text format and your expected result with backend logic and special examples? By the way, is there any relationship among these three tables? If yes, please also provide the related info. It would be helpful to find out the solution. You can refer the following link to share the required info:

How to provide sample data in the Power BI Forum

And It is better if you can share a simplified pbix file. You can refer the following link to upload the file to the community. Thank you.

How to upload PBI in Community

Best Regards