Here’s what I think is happening. I don’t think it’s a bug, we just changed the way we added time zones to observations the other week.
Many of your observations have no time entry (which is totally fine). eg https://www.inaturalist.org/observations/73186191, which was uploaded last year:
In those cases, I think we would use your account’s time zone as the “time zone” - CET - for the observation, which you can see at https://www.inaturalist.org/observations/73186191.json
And that time zone is what’s displayed on the “Added” column in Explore’s list view. Which is why you see CET in that screenshot.
Now, thought, we use the coordinates of the observation to determine its time zone, even if it has no time. So for https://www.inaturalist.org/observations/113023758, which you just uploaded, the observation’s time zone is in Iranian Standard Time: https://www.inaturalist.org/observations/113023758.json
You could make a case for whether we should be displaying the Added time in the observation’s time zone, but it’s not a bug, it’s designed that way. What changed was how we deal with time zones, espeically for observations without any time information filled out.