Acceptable date and timestamp formats for profile and event properties

Learn acceptable date and timestamp formats for profile properties added via API or CSV upload.

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This guide applies to Klaviyo's v1/v2 legacy APIs

We are in the process of updating these guides, please check back later! For more information about the differences between legacy and new APIs, check out the comparison chart and new API overview.

Acceptable date and timestamp formats

When adding an event or profile property to Klaviyo via API or CSV file upload, you must use one of the recognized formats outlined below. Event timestamps sent via the Track API must always be formatted in unix time in seconds.

See the example below for information around formatting your date and timestamps in a CSV file or API call. You must format dates as either YYYY-MM-DD or MM/DD/YYYY. Note that dates cannot be formatted in the DD-MM-YYYY format. If there is no time of day associated with your date, you can set it to midnight by using the HH:MM:SS value 00:00:00.

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If you do not include the hour, minute, or second on your timestamps the values will default to 0. For example, a timestamp of 2021-09-15 13:34 would be submitted to Klaviyo as 2021-09-15 13:34:00. A timestamp of 2021-09-15 would be submitted to Klaviyo as 2021-09-15 00:00:00.

For example, the date September 15th, 2021 at 1:34:08 p.m. should be formatted using one of the following supported formats:

2021-09-15 13:34:08
2021-09-15 13:34:08+00:00
09/15/2021 13:34:08
09/15/21 13:34:08
09/15/2021 13:34
09/15/21 13:34
2021-09-15T13:34:08
1631712848 (Unix)

If you need help reformatting your dates in a spreadsheet before uploading your CSV file, head to our article, Format dates for CSV files.

Note that when you import dates with timestamps this field maps to the date data type. However, when you import a date without a timestamp, a default time of midnight UTC is applied to the date when mapped to the date data type. This may cause date-property triggered flows to send a day early or late depending on the account’s timezone. For that reason, if you only have the date (with no timestamp) to upload, we recommend amending a timestamp of 12:00:00 for the best outcome in a date-property triggered flow.

For more information on uploading a CSV file to Klaviyo, head to our article on how to add subscribers to an existing list.

Additional resources