What values can I send to date fields when adding/updating content via API?

For extended fields (ext_X) whose field setting in the content structure is "Date picker", send a string that can be interpreted as a date.
Endpoints that add or update content such as Topics::insert, Topics::update, and Topics::bulk_upsert, the management APIs, and the topics-create / topics-update tools of Admin MCP handle the value as follows.

Value sent	Result
A string that can be interpreted as a date Ex.) 2026-12-25, 2026-12-25 09:15, 2026-12-25T09:15:00+09:00	Saved as that date and time.
Empty string ""	The field is cleared.
null	The field is cleared. If the field is required, a required-field error is returned.
A string that cannot be interpreted as a date Ex.) unknown, 2026年12月25日	An input error is returned and the record is not saved.Release version: β / RCversion
A single value sent to a repeatable field	Stored in the first repeat slot; the remaining slots are cleared.
An array shorter than the number of slots sent to a repeatable field	The slots that were not sent are cleared.

When "Also include time (hh:mm)" is disabled in the field settings, the time portion of the value is truncated and only the date is saved.

{
  "subject": "Sample",
  "ext_1": "2026-12-25",
  "ext_2": "2026-12-25T09:15:00+09:00",
  "ext_3": ""
}

Related documents

• List of field settings available in content structure - Date picker
• Can I specify related data by slug when adding/updating content via API?
• Can I update image and file fields with the bulk_upsert API for content?
• Admin MCP reference