In your account, on the Preferences page, the Relative/Absolute time preference has been removed. In its place are two new preferences, for how dates and times are displayed. You can display times either in standard format, or in military (24 hour) time. And dates you can display either MM/DD/YYYY or DD-MM-YYYY.
Dates formatted this way only shows up for dates that are older than this year. Otherwise, we continue to use 'Month Day' or, for something that happened on the current day, just the hour and minute (the complete date/time is available by hovering over the date). The calendar does respect the new date preferences.
At some point I will also add these preferences to the default sub settings for groups, but this was already a big change, and I wanted to wait and let the dust settle before I do that.
These changes touched every part of the website. I think I got all instances of dates and times, but there's a chance I missed some. Please let me know if you see any incorrectly formatted dates/times, and please let me know if you have any questions.