We're sorry Aspose doesn't work properply without JavaScript enabled.

Free Support Forum - aspose.com

Error reading XLSX: String was not recognized as a valid DateTime

Scenario: I try to open attached XLSX file to convert it to PDF. Aspose.Cells 18.6

Issue: FormatException is thrown saying “String was not recognized as a valid DateTime”.


  • Issue is caused by the DateTime format of the dateTime attribute of the x:header element in the “xl\revisions\revisionHeaders.xml” OpenXml part.

  • It seems that Aspose.Cells does not like “Z” at the end, because there is no error if I manually remove it.

  • Microsoft Excel may read both formats - w/ and w/o “Z”.

  • The value of the dateTime attribute was set using OpenXml SDK (not by manual manipulation with XML file in text editor), so I think it would be good for Aspose.Cells to support both formats.

     header.DateTime = DateTime.Now;

sample.zip (7.1 KB)


We were able to observe the issue but we need to look into it more. We have logged the issue in our database for investigation and for a fix. Once, we will have some news for you, we will update you in this topic.

This issue has been logged as

CELLSNET-46195 - Converting attached XLSX to PDF raises exception


Thanks for using Aspose APIs.

This is to inform you that we have fixed your issue CELLSNET-46195 now. We will soon provide the fix after performing QA and including other enhancements and fixes.

Thanks for an update. Waiting for a new version.


Thanks for using Aspose APIs.

Please download and try the following fix and let us know your feedback.

Works on my sample file.

  1. Is 18.6.2 an official release?
  2. Did it pass regression testing (or only fixed bugs were tested)?
  3. If it has not been officially released, when it is going to happen?

Many thanks


Thanks for using Aspose APIs.

It is not Official Release. It is a Hot Fix. Official Release consists of two numbers separated by dots. Hot Fix contains three numbers instead.

So, 18.6 and 18.7 are Official Releases but 18.6.3 or 18.7.5 are Hot Fixes.

Hot Fixes are shared via Forums while Official Releases are shared via NuGet

Hot Fixes are well-tested and it is safe to use them in your Production Environment.

The next Official Release 18.7 which will also contain your fix will be published on NuGet around 18-20th July, 2018.

The issues you have found earlier (filed as CELLSNET-46195) have been fixed in Aspose.Cells for .NET v18.7. Please also check the document/article for your reference: https://docs.aspose.com/display/cellsnet/Installation

The issues you have found earlier (filed as ) have been fixed in this update. This message was posted using BugNotificationTool from Downloads module by MuzammilKhan