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Frequent Visitor

Setting Null Value for Date/Time Columns in Flow

Hi all,

Does anyone know a workaround for setting null values in a date/time field in Sharepoint? I'm importing in dates from Excel, using an expression to evaluate if a cell is empty after a filter query. If it is, I set the value as null - however I get the error: The runtime value '""' to be converted doesn't have the expected format 'String/date'.


The expression in question is this: 


 I've also tried replacing null with '' so it returns a blank, this doesn't work either. Nor does string(null). I really don't want to put a dummy date in, preferring a blank value if possible. Any ideas?

Most Valuable Professional
Most Valuable Professional


I suspect that your calculation is not necessary.   In the Excel action, go to advanced settings and set the Dat/Time format to ISO 8601.  That way, you will have a date returned from Excel instead of a serial number.



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Hi Scott,


This was already set in the Excel action, however it still pulls a serial number through. However the null value is still causing me issues. The column is set up to allow null values in Sharepoint, but I can't action it in the flow for some reason?

Community Support
Community Support

Hi @iali4 :

I suspect that the error has nothing to do with SharePoint. As you said, the error content is: The runtime value'""' to be converted doesn't have the expected format'String/date'.

I suspect that there may be a non-date format string in your Date field causing an


I suggest you try this formula and check if the problem is solved.


Best Regards,


Frequent Visitor

Hi @v-bofeng-msft 


Thanks for the advice. Couple of things, I think you may have added a couple of extra end parentheses in there, so I corrected. This unfortunately doesn't solve the problem. Reason being is the if statement is returning a true value for the first argument to evaulate which if the field is empty. So the replace function is redundant as there is nothing in the field in the first place. As the argument returns null from the empty function, this is where '""' originates.


My guess is that null itself is not a string. I've tried initialising a variable with an empty string value to replace with null with and I'm still getting the same error. My thinking is that the date/time columns don't accept any empty values in Power Automate. But there must be a workaround. Blank dates are a must as I use the blank values in calculations for other fields.


Hope this all makes sense!



Frequent Visitor

I've just encountered something strange. By enabling experimental features in Power Automate, the flow now successfully runs with my original expression? This makes no sense, but I'm glad it works now. However this still doesn't explain why it won't work with null values by default?


-- EDIT: Experimental is truly the word. For some inexplicable reason, it's stopped working again, resorting to the default null error. I can't even recreate the successful run I had before 😞 Truly is frustrating.

Frequent Visitor

I'm battling this as well - I'm seriously considering recreating my "create item" action in SharePoint under a conditional for each date field validation, e.g. if value, do sharepoint post, if not value, do identical sharepoint post with nothing entered against that field....

Frequent Visitor

Found a workaround!

I did a conditional validation on the date variables 'inline' above using 'configure run after', where I set the value to 0 if the first attempt to set the date/string fails. Then in the SharePoint field, I used

if (equals(variables('Whateverdate'),0),null,variables('Whateverdate'))

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