Localize dates in Jekyll template without specifying timezone offset

tz_local.rb

# A tiny Jekyll filter for giving custom dates a proper timezone offset
# example usage `{{ post.startDate | tz_local | date: '%l:%M %P'}}`
# Why? If you omit a timezone offset, Jekyll automatically adds +0000...which is probably not what you want. 
# This let's dates like `startDate: 2015-1-14 18:00:00` render correcty in local time. DST is calculated correctly
# NOTE: This will still inherit Jekyll's timezone property as set in _config.yml

module TZLocal
  def tz_local(input)
    input = input + (Time.parse(input.to_s).gmt_offset) * -1
  end
end

Liquid::Template.register_filter(TZLocal)

Thank you for this snippet. Should really be part of Jekyll in my opinion.