I’m trying to use Update a task to update a d```ate_value custom field in an Asana task. The date field is special, in that it consists of 2 values when the task is obtained via GET:
"date_value": {
"date": "2023-09-11",
"date_time": null
}
I’ve tried using the same when updating the task (PUT request: Update a task), but I always get a date_value: DayAndDateTime is not a JSON object error.
The docs on date custom fields (Custom fields) are not clear in how date values need to be formatted, and how a date value should be entered in the CUSTOM_FIELDS OBJECT at Update a task (see attached).

In other words, what string to do I use in the CUSTOM_FIELDS OBJECT section of Update a task to update a date value in a task?
I’ve tried:
- 2023-09-18
- 2023-09-18T00:00:00.000
- { “date”: “2023-09-18” }
- { “date”: “2023-09-18”, “date_time”: null }
All result in the following error: "date_value: DayAndDateTime is not a JSON object:
Hi @Nick_Youngblut,
Here is the correct format:
“custom_fields”: {
“123456789”: {“date”:“2022-08-18”}
}
where “123456789” is the gid of the date custom field.
If your value contains a time component, then it would be
“custom_fields”: {
“123456789”: {“date_time”:“2022-08-18T09:20:32.000Z”}
}
Thanks @Phil_Seeman!
Maybe it would be useful to provide that info in the docs on custom fields? … and/or in the API docs?
I agree! Pinging Asana here: @John_Vu @Andrew-asana
Thanks @Phil_Seeman for helping @Nick_Youngblut out.
I have gone ahead and sent a PR to update our custom field update descriptions.
FROM:
"{custom_field_gid}" => Value (Can be text, number, etc.)
TO:
"{custom_field_gid}" => Value (Can be text, number, etc.). For date use format "YYYY-MM-DD" (EX: 2019-09-15). For date-time use ISO 8601 date string in UTC (EX: 2019-09-15T02:06:58.147Z)
@Nick_Youngblut Hope this makes it more clear. If you would like us to re-word it let us know.