Oh we both see the same thing. But something is off on your server in regards to the dates.

See this: www.threecatsmarketing.com/component/k2/date/2021/3 (no K2 items, yet the title is again set one month back)

In K2, this is the part that controls the title output: github.com/getk2/k2/blob/master/components/com_k2/views/itemlist/view.html.php#L410-L437

Is there any chance some part of your site's code is renaming the months or something? Some plugin? Or some weird language override? It is surely not the template because calling the same URLs with ?template=protostar at the end results in the same issue.

For reference, change the months here: demo.getk2.org/component/k2/itemlist/date/2012/3?template=protostar

You'll see that URLs and actual displayed months are in-sync.

Do check your server's time/date as well.

Genuinely weird.

I'm regretting I haven't added GIF support in this forum :D

I honestly have no idea. Could be some other plugin messing up the timezone.