I checked and it looks like your site uses a customized event list template. There may be the wrong date function being used in that template. Would you be able to share a copy of the template code so we can take a look?
Your site is using EE4 but your event listing looks exactly like EE3’s event list so there has to be something custom here as EE4 events use your site’s theme to output the events so they tie in with the rest of the site. EE3 uses its own templates that don’t look anything like what a theme would use.
Can you link me to the page so we can confirm we are talking about the same location? (You can set you reply private if preferred)