First, could you tell me on which timezone your Joomla configuration is set ?
And secondly, is it possible to have an online link to the page, as you don't use an iCagenda core theme design, so maybe you have one override in your site template, or did a custom theme pack, but the date is now well manage (and with a wrong timezone applied to an already good date, changing the date displayed...)
Latest version : 3.7.9
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