Hello,
I'm not aware of the Spark plugin, would you give me a link to the location where you found this plugin?
One suggestion that I do have for your time zone issue is to use profile fields. You can add custom profile fields in the Admin Console under People > Settings > Profile and Homepage. You can make them required if you like so that all members will have them. You might have the new field added automatically to the pop-up profile as well. Even if it doesn't add the field automatically, it'll probably be much easier to get the field and add it to the pop-up profile with a customization if you make a profile field for it. I hope that helps, and let me know if you have anymore questions.
Thanks,
Kevin