The Coda API has so far returned datetime and date values in Pacific time. These both use ISO-8601 datetime strings including timezone offsets, so technically all of the information was available to recover a value in whatever timezone was desired, but it certainly wasn’t intuitive and involved extra hassle.
Starting this coming Monday, September 26, the API will begin returning datetime and date values in the timezone of the doc instead of Pacific time. These are still ISO-8601 datetime strings with timezone offsets, so the underlying UTC values are not changing. The returned strings should just better match user expectations. We hope that not many cases are relying on the old quirky datetime output that cannot be easily updated.