diff --git a/lib/subroutine.rb b/lib/subroutine.rb
index 85b56c4..828fd72 100644
--- a/lib/subroutine.rb
+++ b/lib/subroutine.rb
@@ -3,3 +3,17 @@
 require "subroutine/version"
 require "subroutine/fields"
 require "subroutine/op"
+
+module Subroutine
+
+  def self.preserve_time_precision=(bool)
+    @preserve_time_precision = !!bool
+  end
+
+  def self.preserve_time_precision?
+    return !!@preserve_time_precision if defined?(@preserve_time_precision)
+
+    false
+  end
+
+end
diff --git a/lib/subroutine/type_caster.rb b/lib/subroutine/type_caster.rb
index 50a2130..8a23ed8 100644
--- a/lib/subroutine/type_caster.rb
+++ b/lib/subroutine/type_caster.rb
@@ -4,6 +4,8 @@
 require 'time'
 require 'bigdecimal'
 require 'securerandom'
+require 'active_support'
+require 'active_support/json'
 require 'active_support/core_ext/date_time/acts_like'
 require 'active_support/core_ext/date_time/calculations'
 require 'active_support/core_ext/object/acts_like'
@@ -111,7 +113,7 @@ def self.cast(value, options = {})
   t ||= value if value.is_a?(::Time)
   t ||= value if value.try(:acts_like?, :time)
   t ||= ::Time.parse(String(value))
-  t.utc.iso8601
+  t.utc.iso8601(::ActiveSupport::JSON::Encoding.time_precision)
 end
 
 ::Subroutine::TypeCaster.register :date do |value, _options = {}|
@@ -123,21 +125,16 @@ def self.cast(value, options = {})
 ::Subroutine::TypeCaster.register :time, :timestamp, :datetime do |value, options = {}|
   next nil unless value.present?
 
-  if options[:precision] == :high
-    if value.try(:acts_like?, :time)
-      value.to_time
-    else
-      ::Time.parse(String(value))
-    end
-  else # precision == :seconds
-    time = if value.try(:acts_like?, :time)
-      value.to_time
-    else
-      ::Time.parse(String(value))
-    end
-
-    time.change(usec: 0)
+  value = if value.try(:acts_like?, :time)
+    value.to_time
+  else
+    ::Time.parse(String(value))
   end
+
+  # High precision must be opted into. The original implementation is to set usec:0
+  next value if options[:precision] == :high || ::Subroutine.preserve_time_precision?
+
+  value.change(usec: 0)
 end
 
 ::Subroutine::TypeCaster.register :hash, :object, :hashmap, :dict do |value, _options = {}|
diff --git a/lib/subroutine/version.rb b/lib/subroutine/version.rb
index 3efc3fd..1889eff 100644
--- a/lib/subroutine/version.rb
+++ b/lib/subroutine/version.rb
@@ -4,7 +4,7 @@ module Subroutine
 
   MAJOR = 3
   MINOR = 0
-  PATCH = 4
+  PATCH = 5
   PRE   = nil
 
   VERSION = [MAJOR, MINOR, PATCH, PRE].compact.join(".")
diff --git a/test/subroutine/type_caster_test.rb b/test/subroutine/type_caster_test.rb
index 9ad4e13..3d05f98 100644
--- a/test/subroutine/type_caster_test.rb
+++ b/test/subroutine/type_caster_test.rb
@@ -316,6 +316,20 @@ def test_time_inputs__with_seconds_precision
       assert_equal 0, op.time_input.usec
     end
 
+    def test_time_inputs__with_preserve_time_precision
+      Subroutine.stubs(:preserve_time_precision?).returns(true)
+
+      time = Time.at(1678741605.123456).utc
+      op.time_input = time
+      assert_equal 2023, op.time_input.year
+      assert_equal 3, op.time_input.month
+      assert_equal 13, op.time_input.day
+      assert_equal 21, op.time_input.hour
+      assert_equal 6, op.time_input.min
+      assert_equal 45, op.time_input.sec
+      assert_equal 123456, op.time_input.usec
+    end
+
     def test_time_inputs__with_high_precision
       op.precise_time_input = nil
       assert_nil op.precise_time_input
@@ -410,11 +424,11 @@ def test_iso_time_inputs
 
       op.iso_time_input = '2022-12-22T10:30:24Z'
       assert_equal ::String, op.iso_time_input.class
-      assert_equal '2022-12-22T10:30:24Z', op.iso_time_input
+      assert_equal '2022-12-22T10:30:24.000Z', op.iso_time_input
 
-      op.iso_time_input = Time.parse('2022-12-22T10:30:24Z')
+      op.iso_time_input = Time.parse('2022-12-22T10:30:24.123456Z')
       assert_equal ::String, op.iso_time_input.class
-      assert_equal '2022-12-22T10:30:24Z', op.iso_time_input
+      assert_equal '2022-12-22T10:30:24.123Z', op.iso_time_input
     end
 
     def test_file_inputs