Here, assuming you use the nice json parser
Code:
alias twitch_uptime {
  JSONOpen -ud Twitch_Uptime https://api.twitch.tv/kraken/streams/ $+ $mid($1,2)  
  return $json(Twitch_Uptime,stream,created_at)
}


You can $twitch_uptime(#channelname) and format the response however you like.