Bryce thinks globally, posts locally:

Radio's date / time macros need to be configurable. For starters, the timestamps in my posts should be configurable to include the timezone and GMT offset. The Internet audience is global, it's natural to expect that many of my readers will be in another timezone and not be aware of which timezone my content was created in.

There are people who want 24-hour times, as discussed here and here.

Months ago, Ingo Rammer pointed out the issues of using Radio to publish an English-language web site from a German version of Windows.

Ideally, Radio would default to using the regional settings as specified by the OS. I don't mean "It's German windows, we'll use German day names." Windows has a "Regional and Language options" control panel that lets the user specify any language and use any format, and there are APIs to handle the dirty work (presumably Mac OS has something similar). Radio should respect those exact settings, and provide an easy way to override them.

TZ offsets are an acknowledgement of the global nature of the Internet. Most Internet RFCs require either offsets or that GMT be used whenever time data is exchanged.

Blogs are chronological, so let's get time presentation right.

Follow up:

I'd also like to see better support for calendaring.

• Radio is unfriendly to non-Julian calendars. Almost hostile to Japanese, Chinese, Indian, Islamic, and Jewish calendars. They are used by a quarter of the world's population. Blogging will difuse into non-Eurogenetic cultures; Radio will lead only if it covers localization basics.  
  
• Refactor the Radio calendar navigation design. Start with a blank white board and brainstorm representations of the blog flow.
• How can we zoom more than previous/next month? It's August and I want to go back 12 months, I have go through 11 wasted months.
• Allow navigation over an empty month.
• Correct the calendar navigation when archive files changed.
• Eliminate the screen waste of days where nothing is posted.
• How can we show some days more attractive than others? (More visits? More in-links? More content, more words?) 
• Option to archive by post instead of by day.
   
• Support the vCal/iCal and related specs.
• Allow the simple entry and presentation of events.
• Enable syndication and aggregation of events, perhaps wrapped in RSS.
• Support importing many events by watching a folder or on command. Great to import events from Microsoft Project or Outlook, each into their own post.
• Have a separate set of attributes for event start and end dates/times associated with a post.
• Allow for sorting of a category by event date, not post date. This should be a category rendering preference.  Bonus points: category home page can be set to show only future events.  So updates flow across my home page as I write them but the "Coming Events" category orders them by event date.
• Make sure this works with the MultiAuthor weblog. Collective calendaring.
• Support drag and drop of vCal objects to and from a post.
• Tool to maintain ComingEvents.opml.  

[aka Blue Sky Radio]