I'm fairly new to SharePoint and have been wrestling with this particular problem for some time now. Whenever I try using the REST API for a calendar list using the following url


it fails and returns the following:

 <m:code>-1, System.FormatException</m:code> <m:message
 xml:lang="en-US">Input string was not in a correct format.</m:message>

The same format for all the rest of my lists that are non calendar type work just fine. I know I am not misspelling the list name and it does exist. I feel that there is something fundamentally wrong. Is there something special that I need to do for the calendar type list?

Any help to point me to the right direction will be greatly appreciated.

  • Have you tried /_api/web/lists(guid'list GUID')? Just for testing
    – cubanGuy
    Feb 24, 2015 at 17:58
  • If he title of the list contains a space you can leave it as ('Class Sessions') and will work. Feb 25, 2015 at 15:12
  • Awesome! It work to perfection. Although I do wonder why it was a problem in the first place? Feb 26, 2015 at 13:41

3 Answers 3


I faced this scenario, and the problem was related to a incorrect Field definition.


Late reply, but still may be useful for someone:

I've noticed %20 in input string - please be aware that SP marks spaces as 'x0020', so 'Class_x0020_Sessions' should work.

TIP: Underscore is marked as 'x005f'


I still don't know what the problem was exactly but Cubanguy's suggestion worked just fine. Instead of using the getByTitle('ClassS')/fields read operation I used _api/web/lists(guid'<list id>').

It was a simple fix to an odd problem. Thank you!

  • I am facing the same issue, while i Use rest to get a list data in my client web-part / App-Part in SP2013 i get the same error. Sep 21, 2015 at 6:52

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