Truncate Dates in Excel Files Online
Truncate date and timestamp columns in Excel files to a chosen precision — year, quarter, month, week, day, hour, or minute — directly in your browser. Rounds timestamps down to the start of each period. No upload required.
How to truncate Dates in Excel files
- Drop your file onto the upload area. The first date or timestamp column is selected for you, and the first 200 rows are shown.
- Check the "Column to truncate" choice. Each column is listed with its detected type, so you can see whether it loaded as a date, a timestamp or text.
- Pick the precision under "Truncate to": year, quarter, month, week, day, hour, minute or second. Month is the default.
- Choose "Replace column in place", or "Append as new column (keeps original)" and give the new column a name. The default name is the column name plus _trunc.
- Click Truncate Dates, check the preview, and download the result in the same format you uploaded.
Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.
Worked example
A support team exports ticket open times and wants a week column to count tickets per week in a pivot table, while keeping the exact open time for reference.
Input (Excel)
Excel workbook, first sheet (Sheet1)
| ticket_id | opened_at | priority |
|---|---|---|
| T-101 | 2026-06-03 14:20:00 | high |
| T-102 | 2026-06-07 23:59:00 | low |
| T-103 | 2026-06-08 08:05:00 | medium |
| T-104 | 2026-06-12 17:40:00 | high |
| T-105 | NULL | low |
Settings
- Column to truncate: opened_at
- Truncate to: Week (Monday, as a date)
- Output mode: Append as new column, named opened_week
Result
| ticket_id | opened_at | priority | opened_week |
|---|---|---|---|
| T-101 | 2026-06-03 14:20:00 | high | 2026-06-01 |
| T-102 | 2026-06-07 23:59:00 | low | 2026-06-01 |
| T-103 | 2026-06-08 08:05:00 | medium | 2026-06-08 |
| T-104 | 2026-06-12 17:40:00 | high | 2026-06-08 |
| T-105 | NULL | low | NULL |
Weeks start on Monday, so Wednesday 3 June and Sunday 7 June both fall in the week of Monday 1 June. A ticket opened a few minutes after midnight on Monday 8 June starts the next week. The missing open time stays empty. For year, quarter, month, week and day the new column holds plain dates. Hour, minute and second keep a time part.
Working with Excel files
Excel keeps dates as serial numbers with a display format. For cells with a date format, the tool uses the stored value, not the displayed text. A date shown as 3/2/26 or 02-Mar-2026 arrives as 2026-03-02, and a date-time as 2026-03-02 09:45:00, so the column loads as a timestamp and truncates cleanly. Times hidden by the cell format are still there, which matters for the hour unit.
Two cases still come back empty. A date typed as text, such as 1-Jun-26 with a leading apostrophe, is not a timestamp, so run Parse Dates on it first. A date left in General format is a plain serial like 46083, so set a date format in Excel and upload again. Truncated dates are written back to the .xlsx as text in 2026-06-01 form, not as Excel date cells, so Excel date filters will treat them as text until you convert them with Data > Text to Columns. For grouping in a pivot table, text in ISO order still sorts correctly. Only the first sheet of your workbook is processed, and the downloaded workbook has one sheet, Sheet1, with the other columns in their original order.
Frequently Asked Questions
Why are my Excel timestamps empty after truncating?
The cells are probably text or plain numbers, not real Excel dates. Real date cells load as timestamps whatever their display style. Run Parse Dates on text dates, or give serial numbers a date format in Excel, then upload again.
Will Excel recognise the truncated values as dates?
They are written as ISO text, like 2026-06-01. Excel sorts them correctly, but you need Text to Columns or DATEVALUE to turn them back into real Excel dates.
What day does a truncated week start on?
Monday. Week truncation follows ISO weeks, so every value from Monday 00:00 to Sunday 23:59:59 maps to that Monday.
Does truncating round to the nearest period?
No. It always rounds down to the start of the period. 2026-06-30 23:59 truncated to month is 2026-06-01, not 2026-07-01.
What happens to values that are not valid dates?
They become empty (NULL) in the output. The run does not fail, so compare the number of empty cells before and after to spot parsing problems.
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