Fix SharePoint Online Date and Time Fields Showing 01/01/1970
Question details
Users report that specific Date and Time columns in a SharePoint Online list automatically default to 01/01/1970 00:00 when items are created or edited.
- Product
- SharePoint Online
- Device & OS
- not provided
- Scenario
- Creating or modifying items in a SharePoint list using the default form.
- Observed behavior
- Start Time and End Time columns automatically populate with 01/01/1970 00:00, despite having no Power Automate flows writing to those fields.
Ensure you have Site Owner or List Administrator permissions in SharePoint Online to access list settings, review column configurations, and inspect default forms.
Review Column Settings and Rename Temporarily
Identify if the issue is tied to the specific column name or hidden column-level calculations by temporarily renaming the affected fields.
Sometimes hidden background scripts or calculations explicitly target specific column names like 'Start Time' or 'End Time'. Changing the name temporarily helps isolate whether the issue is attached to the column's configuration or its display name.
Navigate to your SharePoint List, click on the Settings gear icon in the top right corner, and select 'List settings'.
Scroll down to the 'Columns' section and click on the affected Date and Time column. Verify that the 'Default value' is not set to a calculated value or an erroneous hardcoded date.
Temporarily change the 'Column name' (for example, to 'Start Time 1') and click 'OK' to save your changes.
Return to the list and create a new item to see if the 01/01/1970 date still appears. If the issue stops, a hidden script may have been targeting the original name.
Inspect for Hidden Form Customizations
Check if Power Apps customizations or injected form scripts are inadvertently passing blank date values.
Compare with New Columns and Contact Support
Determine if the list schema is corrupted by testing new columns, and escalate to Microsoft if it is a backend service issue.
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Frequently Asked Questions
Why does SharePoint default to the date 01/01/1970?
The date 01/01/1970 is the standard Unix epoch time (the starting point for computer time). When a system, script, or custom form passes a null, blank, or invalid date value to a SharePoint Date and Time field, the system cannot interpret it and falls back to this default epoch date.
Can Power Automate cause this 1970 date issue even if it's not meant to write to the column?
Yes. If a Power Automate flow reads a list item and uses the 'Update item' action to change other fields, it might inadvertently pass empty variables back into the date fields. This overwrites the existing data with a null value, triggering the 1970 epoch date.
How do I fix the 1970 date error in a Power Apps customized SharePoint form?
In Power Apps, check the DefaultDate property of the DatePicker control. If it evaluates to Blank(), you can use a formula like If(IsBlank(Parent.Default), Blank(), Parent.Default) to ensure it handles empty states correctly without sending a null value that SharePoint interprets as 1970.
