date format display incorrect

Hi, I found the dates to be displayed incorrectly. They are shown with this formatting which does not allow them to be displayed correctly. Can you tell me where to intervene to resolve the problem? I've seen that in all the plugins that use the data it is shown badly. I thank everyone in advance.

At the moment I get a display like this: aa-01-gg

using elgg 6.1.1

Sorry for my English, but it's not my native language

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