I have tried setting my date field to an empty string ("") and setting it to "01/01/0001". Both returned the error "String is not formatted as date time". I have several thousand items across a few subsites which mistakenly received some December date, and I'd like those to be set to empty.

Workflows have proven to take too long for this process, and I already have a C# utility written to update all fields that I specify (e.g., "set "Modified By" on all items with ID > 500 to [My Name]"), but I cannot seem to find a way set a date field back to empty.

  • Can you share your code? Try setting the date to null instead of an empty string.
    – Mike
    Jul 21, 2014 at 18:52
  • It's a part of a longer utility. I set date fields in the following format: ` item["Modified"] = Convert.ToDateTime("01/01/0001");
    – Dinerdo
    Jul 21, 2014 at 18:54
  • 1
    Try item["Modified"] = null;
    – Mike
    Jul 21, 2014 at 18:55

1 Answer 1


Try item["Modified"] = null;

That should make the Date/Time field empty.

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