Ignore DST on Rails Timzone - ruby-on-rails

Question

I receive time-stamped data from some equipments, who are configured with a timezone (Europe/Paris, for example).
Problem is that some of them are not aware of DST (Daylight Saving Time) change, and some are, which causes us to have a offset problem when we're in DST (like right now).
Today I have the following code to parse this data:
def parse_timestamp(timestamp, format=nil)
case timestamp
when String then #timezone.local_to_utc(Time.strptime(timestamp, format))
when Integer then #timezone.local_to_utc(#timezone.at(timestamp))
else raise Etl::Parsers::TimeConversionError, "Can't parse timestamp #{timestamp.inspect}"
end
end
The #timezone variable is created like this: ActiveSupport::TimeZone[timezone].
I'm looking for a way to ignore the DST when the equipment have a #dst property (let's say) that tells wether its timestamps are DST aware.

Answer 1

ActiveSupport::TimeWithZone has a useful dst? method to check if the time is within Daylight Savings Time for the specified time zone:
Time.zone = 'Eastern Time (US & Canada)' # => 'Eastern Time (US & Canada)'
Time.zone.parse("2012-5-30").dst? # => true
Time.zone.parse("2012-11-30").dst? # => false
You can read more at http://api.rubyonrails.org/classes/ActiveSupport/TimeWithZone.html#method-i-dst-3F
So you can just check if time is within DST, or extend TimeWithZone, as explained here Make Rails ignore daylight saving time when displaying a date by #zeantsoi:
class ActiveSupport::TimeWithZone
def no_dst
self.dst? ? self - 1.hour : self
end
end
and use it this way always getting the time without DST:
time.in_time_zone("Eastern Time (US & Canada)").no_dst