I am in time zone utc+10. If I subtract 10 hours from the desired alert time it posts the correct utc time. This usually means subtracting a day too, whenever my desired alert time is less than 10:00 utc.
Users in zones that are utc minus X may also have to adjust their alert times with this app. Which way, I don't know. Possibly the same as I do.
This problem commenced with an app update aBout 18 months ago.
I experimented with alerts a week out from the current date to avoid confusing others. Afterwards I logged in from my PC and deleted all the test alerts.
73 Andrew VK1DA VK2UH