Date-Time parsing problem

Question

The following ISO formatted date-time fields fail on 3rd and 7th lines. As far as I understand from my trials if millisecond's part starts with 0, then the parser fails to detect text as a valid date-time field.

(Microsoft® Excel® for Microsoft 365 MSO (Version 2606 Build 16.0.20131.20152) 64-bit)

2026-07-10 13:40:08.360

2026-07-10 13:40:18.163

2023-10-17 10:18:31.080

2024-05-29 13:00:09.307

2024-05-29 18:44:48.410

2026-06-17 11:46:36.900

2026-06-17 11:46:40.010

2026-05-22 11:07:46.827

2026-04-28 11:11:47.877

2026-04-28 09:28:29.920

Answer 1

Hi,
Thank you for providing the sample values.

I reviewed the information you shared. Based on the data alone, there isn't enough information to determine why only some of the values are not recognized.

Microsoft documents that Excel does not support all ISO 8601 date/time formats in every import scenario, particularly formats that include fractional seconds. You can find the documentation here: XML Schema Definition (XSD) data type support | Microsoft Support

There is also a Microsoft Q&A discussion covering ISO date/time recognition in Excel: Excel does not recognize ISO formated date time (yyyy-mm-ddTHH:MM:ssZ) - Microsoft Q&A

To help identify the cause, could you please provide the following information?

• How are these values being brought into Excel (copy/paste, opening a CSV file, Power Query, or another import method)?
• What is the expected result, and what happens on the rows that fail?

With this information, I can further investigate whether the behavior is related to the import process or whether additional investigation is needed.