Fix timestamp failures

Author: jterapin

gems/smithy-schema/lib/smithy-schema/time_helper.rb

@@ -5,6 +5,7 @@ module Schema
     # A module that provides helper methods to convert Time objects
     # based on the given TimestampFormat trait.
     # @api private
+    # TODO: need to handle fractional secs
     module TimeHelper
       class << self
         # @param [Time] time

gems/smithy-schema/spec/smithy-schema/time_helper_spec.rb

@@ -7,18 +7,18 @@ module Smithy
   module Schema
     describe TimeHelper do
       describe '#time' do
-        let(:time) { Time.new(2002, 10, 31) }
+        let(:time) { Time.utc(2002, 10, 31) }
 
         it 'returns as http-date format' do
-          expect(subject.time(time, 'http-date')).to eq('2002-10-31T08:00:00Z')
+          expect(subject.time(time, 'http-date')).to eq('2002-10-31T00:00:00Z')
         end
 
         it 'returns as date-time format' do
-          expect(subject.time(time, 'date-time')).to eq('Thu, 31 Oct 2002 08:00:00 GMT')
+          expect(subject.time(time, 'date-time')).to eq('Thu, 31 Oct 2002 00:00:00 GMT')
         end
 
         it 'returns as epoch-seconds format' do
-          expect(subject.time(time, 'epoch-seconds')).to eq(1_036_051_200)
+          expect(subject.time(time, 'epoch-seconds')).to eq(1_036_022_400)
         end
 
         it 'raises when given time is invalid ' do