Sorry, but the video is not viewable. See info: https://help.imgur.com/hc/en-us/articles/41592665292443-Imgur-access-in-the-United-Kingdom Please provide some info so we can check if there's a bug report and understand all the settings you are using. # What OS are you using ? # What version of Thunderbird are you using? # Where did you get the Thunderbird installation eg: the official Thunderbird website: https://www.thunderbird.net/en-US/thunderbird/all/ Or did you get it via Windows App Store or Flatpak or Snap etc? # What language version of Thunderbird are you using? # What Timezone is computer set up to use? # Did this issue suddenly occur after an update? # Do you use any addons ? Please post info you see in the following location: * 'Help' > 'Troubleshooting Information' * Scroll down to the 'Add-ons' section * Copy all the list and paste it into this forum question. Now check the following whilst still using/seeing the 'Troubleshoot Information' tab. * top right where it says 'Diagnose Issues' - click on 'Troubleshoot Mode' - * Select 'Continue in Troubleshoot Mode' Thunderbird will restart in Troubleshoot mode, so you may see some default settings appear - do not worry about it. * In Calendar, click on 'New Event' * Create a test event. * Please use the drop down to select Month, date * Do the same to select the Time - use the drop down - note you need to select the Hour and the minutes options. Is everything working whilst in Troubleshoot Mode ? Tell us what is set up as default Calendar settings: * Settings > Calendar * Please post a couple of images to show all the current Calendar default settings.