DATETIME_FORMAT dddd offset?

What table? There’s no table in your post. I found a link to a table in your original post (before it was edited), but even after opening that, I don’t see any comments. Can you provide more details about the error you’re seeing? I’m not sure what to look for.

When I see ‘error’ or ‘offset’ in any post dealing with a date or datetime value, my initial assumption is that the poster is receiving a response that shows either the date off by a day or the time off by a number of hours from what he or she expects. Even more irritatingly, in the first instance the problem may not seem reproducible at first or may suddenly disappear during testing. If that is the case here, I suggest you check the current value of the ‘Use the same time zone (GMT) for all collaborators’ configuration toggle for {Premiere - HKT}. If it’s enabled, the response will be off by however many hours your local time zone is offset from UMT.

If you’re receiving a different sort of error — or receiving an #ERROR! message as the result — it might be caused by the evaluation of a date field with an empty string. (In most cases, Airtable will accept a null string — ‘""’ — as interchangeable with a BLANK() field, but not always.) If so, you can modify your formula to read

IF({Premiere - HKT}=BLANK(),'N/A',DATETIME_FORMAT({Premiere - HKT},'dddd'))

or, even better [as a habit, because it bypasses any potential oddity regarding how "", 0, and BLANK() are evaluated], invert the logic of your IF() statement to take advantage of Airtable’s implicit understanding of null and non-null values:

IF({Premiere - HKT},DATETIME_FORMAT({Premiere - HKT},'dddd'),'N/A')

If your trouble is something other than either of these, give us a little more information, and we’ll back up and run it over again.

Thanks for the link to the table, but I’m still not sure what we’re supposed to be looking for. Your original post says “See first comment for the table,” but there aren’t any comments visible. The view you provided doesn’t let us look at the table’s (or base’s) internals like comments, field types, etc.