Displayed start time of the event changes unexpectedly

I see that there is already a bug related to time zone management of email confirmation of events, but this concerns the event page: I’ve created an event set to begin at 16:00, and in Firefox v83 I see it at 16:00 (even if I log out), while in Chrome v86, on the same machine, it tells me it begins at 17:00… Someone else with whom I shared it tells me she also sees 17:00, the wrong start time.

How does the page infer the time zone of the user? And how can I announce the correct time for the event to all my guests? Thank you.


The current datetime in your timezone and your timezone itself is given by your browser (through the Intl.DateTimeFormat API), which in turn should use your system timezone, so it’s odd that Firefox and Chrome give different values here.

However, it seems that in Firefox, if the privacy.resistFingerprinting setting has been changed in about:config, the only timezone given to us is UTC, which might explain your issue (see this bug).

You create events with times in your local timezone, so you’ll have to convert time to UTC next time you want to create an event for it to show properly.

Otherwise maybe we could use the user setting (that we currently use for emails) to try to override the one given by Intl, if they are different? If you have the time to open such an issue, please do!

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Thank you, that is very on-point and correct - I had enabled privacy.resistFingerprinting! Yes, I think that using the user-defined time zone makes most sense, I thought that was (partly) why I was defining it. Actually, one thing I did to try to solve the issue was to add a location to my event, as before it had none, so I thought it depends on that. Facebook does infer the timezone from the location which was something very confusing in the beginning, because they would use very weird ones when no location was defined (as for online events). But I (and, I presume, most people) got used to it. So, to me, it would make most sense to:

  • use the time-zone implied by the event location when it’s defined
  • use the user settings time zone when not
  • tell the user which time zone is being used, either way and
  • ideally, allow organisers to change the time zone manually for each event

This will respect the wishes of those who care about privacy, and give as much control as possible to the event organisers.

Yes, I will create an issue. Thanks again for your help.