backend: format session time blocks as hhmm
backend: format session time blocks as hhmm

mm is removed when 00.

google/ioweb2016,GoogleChrome/ioweb2016,google/ioweb2016,GoogleChrome/ioweb2016,google/ioweb2016,google/ioweb2016,GoogleChrome/ioweb2016,GoogleChrome/ioweb2016