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# Changes for March 14 - 27, 2022

Read about our new changes below.

### Features

* You can now filter databases on the created at and last edited at timestamps, even if they don't have a corresponding property of that type. Read more [here](/reference/post-database-query-filter#timestamp-filter-object).
* A [`Retry-After`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Retry-After) response header is now being sent with rate limited request responses. The value of this field is set as an integer number of seconds (in decimal). Requests made after waiting this minimum amount of time should not be rate limited. Read more about our rate limits [here](/reference/request-limits#rate-limits).

### Bug fixes and performance improvements

* Stopped throwing an error when rendering property formulas that hadn't been set up yet in the [Retrieve a page property item](/reference/retrieve-a-page-property) endpoint. These formulas now return `null` values.