Forum Discussion
Excel auto-truncating timestamps sub milliseconds
I would like to leave feedback. It is very frustrating that when I try to look at logged data csv in excel, I cannot open it by double clicking, because Excel date-time format is so limited. It truncates sub millisecond data (don't save that file - or the data is lost!), so that any graphs start looking like stairs. And the work-around, to import the csv data and change the timestamp column format to text , and then convert it to a number, is very clunky. It forces me to other programs, like Matlab, which many people do not have.
Example data:
Timestamp,V-Output ,I-Output ,V-Normal ,I-Normal ,V-Emergency,I-Emergency,VGND ,IN ,
2025-12-18 00:08:46.730845,
Is it possible that you improve your product?
You're right that Excel truncates sub-millisecond data (microseconds and nanoseconds) because its datetime format only supports precision down to milliseconds .You’re running into a precision limitation in Excel, not just a formatting issue. The stair-step graphs are the telltale sign of lost precision.
Practical Workaround
Instead of double-clicking the CSV (which forces Excel's auto-formatting), set up a proper import that preserves your full timestamps with Power Query Import.
- Open a blank Excel workbook (don't double-click the CSV)
- Go to the Data tab → Get Data → From File → From Text/CSV
- Select your CSV file and click Import
- CRITICAL STEP: In the preview window, find your timestamp column
- Click the data type icon (usually says "ABC" or "Date") next to the column header
- Change it from whatever it auto-detected to "Text"
- Click Load
This brings all your data in exactly as written in the CSV—no truncation, no auto-formatting. Your timestamps like 2025-12-18 00:08:46.730845 will remain intact as text strings.
Considerations…
If you later convert the text to a datetime format in Excel, it may still truncate sub-milliseconds. Excel's native datetime format only supports up to milliseconds (3 decimal places).
Workaround: Keep timestamps as text for storage, and use Python/pandas for analysis where pd.to_datetime() preserves nanoseconds.Use Power Query for storage (import as text) and Python for analysis/visualization. This hybrid approach gives you:
- Data Integrity: Timestamps remain intact in Excel.
- Flexibility: Leverage pandas for high-precision calculations/plotting.
My answers are voluntary and without guarantee!
Hope this will help you.
5 Replies
You're right that Excel truncates sub-millisecond data (microseconds and nanoseconds) because its datetime format only supports precision down to milliseconds .You’re running into a precision limitation in Excel, not just a formatting issue. The stair-step graphs are the telltale sign of lost precision.
Practical Workaround
Instead of double-clicking the CSV (which forces Excel's auto-formatting), set up a proper import that preserves your full timestamps with Power Query Import.
- Open a blank Excel workbook (don't double-click the CSV)
- Go to the Data tab → Get Data → From File → From Text/CSV
- Select your CSV file and click Import
- CRITICAL STEP: In the preview window, find your timestamp column
- Click the data type icon (usually says "ABC" or "Date") next to the column header
- Change it from whatever it auto-detected to "Text"
- Click Load
This brings all your data in exactly as written in the CSV—no truncation, no auto-formatting. Your timestamps like 2025-12-18 00:08:46.730845 will remain intact as text strings.
Considerations…
If you later convert the text to a datetime format in Excel, it may still truncate sub-milliseconds. Excel's native datetime format only supports up to milliseconds (3 decimal places).
Workaround: Keep timestamps as text for storage, and use Python/pandas for analysis where pd.to_datetime() preserves nanoseconds.Use Power Query for storage (import as text) and Python for analysis/visualization. This hybrid approach gives you:
- Data Integrity: Timestamps remain intact in Excel.
- Flexibility: Leverage pandas for high-precision calculations/plotting.
My answers are voluntary and without guarantee!
Hope this will help you.
Don't know why that happens. I log in with the account I use to long in to this forum. Can't help you any further. Sorry!
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