diff --git a/iseq.c b/iseq.c
index 93e58db2e65287..f2db484f59f03e 100644
--- a/iseq.c
+++ b/iseq.c
@@ -3002,6 +3002,10 @@ rb_iseq_disasm_recursive(const rb_iseq_t *iseq, VALUE indent)
         n += rb_iseq_disasm_insn(str, code, n, iseq, child);
     }
 
+    if (body->mandatory_only_iseq) {
+        rb_ary_push(child, (VALUE)body->mandatory_only_iseq);
+    }
+
     for (l = 0; l < RARRAY_LEN(child); l++) {
         VALUE isv = rb_ary_entry(child, l);
         if (done_iseq && st_is_member(done_iseq, (st_data_t)isv)) continue;
diff --git a/lib/time.rb b/lib/time.rb
index e6aab3fa5d444b..1c66088d33ac21 100644
--- a/lib/time.rb
+++ b/lib/time.rb
@@ -369,6 +369,9 @@ def make_time(date, year, yday, mon, day, hour, min, sec, sec_fraction, zone, no
     # If the extracted time zone abbreviation does not match any of them,
     # it is ignored and the given time is regarded as a local time.
     #
+    # A +zone+ argument can be provided to specify the zone for the given
+    # +date+, if the +date+ does not include a time zone or offset.
+    #
     # ArgumentError is raised if Date._parse cannot extract information from
     # +date+ or if the Time class cannot represent specified date.
     #
@@ -382,12 +385,12 @@ def make_time(date, year, yday, mon, day, hour, min, sec, sec_fraction, zone, no
     #
     # You must require 'time' to use this method.
     #
-    def parse(date, now=self.now)
+    def parse(date, now=self.now, zone: nil)
       comp = !block_given?
       d = Date._parse(date, comp)
       year = d[:year]
       year = yield(year) if year && !comp
-      make_time(date, year, d[:yday], d[:mon], d[:mday], d[:hour], d[:min], d[:sec], d[:sec_fraction], d[:zone], now)
+      make_time(date, year, d[:yday], d[:mon], d[:mday], d[:hour], d[:min], d[:sec], d[:sec_fraction], d[:zone] || zone, now)
     end
 
     #
@@ -624,39 +627,84 @@ def httpdate(date)
     # You must require 'time' to use this method.
     #
     def xmlschema(time)
-      if /\A\s*
+      pattern = /\A\s*
           (-?\d+)-(\d\d)-(\d\d)
           T
           (\d\d):(\d\d):(\d\d)
           (\.\d+)?
           (Z|[+-]\d\d(?::?\d\d)?)?
-          \s*\z/ix =~ time
-        year = $1.to_i
-        mon = $2.to_i
-        day = $3.to_i
-        hour = $4.to_i
-        min = $5.to_i
-        sec = $6.to_i
-        usec = 0
-        if $7
-          usec = Rational($7) * 1000000
+          \s*\z/ix
+      _xmlschema(pattern, time)
+    end
+    alias iso8601 xmlschema
+
+    #
+    # Parses +time+ as a dateTime defined by RFC3339 and converts it to
+    # a Time object.
+    #
+    # ArgumentError is raised if +time+ is not compliant with the format or if
+    # the Time class cannot represent the specified time.
+    #
+    # See #xmlschema for more information on this format.
+    #
+    #     require 'time'
+    #
+    #     Time.rfc3339("2011-10-05T22:26:12-04:00")
+    #     #=> 2011-10-05 22:26:12-04:00
+    #
+    # You must require 'time' to use this method.
+    #
+    def rfc3339(time)
+      pattern = /\A\s*
+          (-?\d{4})-(\d\d)-(\d\d)
+          [T\s]
+          (\d\d):(\d\d):(\d\d)
+          (\.\d+)?
+          (Z|[+-]\d\d(?::?\d\d)?)?
+          \s*\z/ix
+      _xmlschema(pattern, time)
+    end
+
+    private
+
+    if RUBY_VERSION >= "3.2"
+      def _xmlschema(pattern, time)
+        if pattern.match?(time)
+          new(time)
+        else
+          raise ArgumentError.new("invalid xmlschema format: #{time.inspect}")
         end
-        if $8
-          zone = $8
-          off = zone_offset(zone)
-          year, mon, day, hour, min, sec =
-            apply_offset(year, mon, day, hour, min, sec, off)
-          t = self.utc(year, mon, day, hour, min, sec, usec)
-          force_zone!(t, zone, off)
-          t
+      end
+    else
+      def _xmlschema(pattern, time)
+        if pattern =~ time
+          year = $1.to_i
+          mon = $2.to_i
+          day = $3.to_i
+          hour = $4.to_i
+          min = $5.to_i
+          sec = $6.to_i
+          usec = 0
+          if $7
+            usec = Rational($7) * 1000000
+          end
+          if $8
+            zone = $8
+            off = zone_offset(zone)
+            year, mon, day, hour, min, sec =
+              apply_offset(year, mon, day, hour, min, sec, off)
+            t = self.utc(year, mon, day, hour, min, sec, usec)
+            force_zone!(t, zone, off)
+            t
+          else
+            self.local(year, mon, day, hour, min, sec, usec)
+          end
         else
-          self.local(year, mon, day, hour, min, sec, usec)
+          raise ArgumentError.new("invalid xmlschema format: #{time.inspect}")
         end
-      else
-        raise ArgumentError.new("invalid xmlschema format: #{time.inspect}")
       end
     end
-    alias iso8601 xmlschema
+
   end # class << self
 
   #
@@ -731,4 +779,5 @@ def xmlschema(fraction_digits=0)
     end
   end
   alias iso8601 xmlschema unless method_defined?(:iso8601)
+  alias rfc3339 xmlschema
 end
diff --git a/test/ruby/test_iseq.rb b/test/ruby/test_iseq.rb
index 30931587f8b6e4..0a06d01b08a1d4 100644
--- a/test/ruby/test_iseq.rb
+++ b/test/ruby/test_iseq.rb
@@ -524,6 +524,12 @@ def test_anon_block_param_in_disasm
     assert_equal [:&], param_names
   end
 
+  def test_disasm_mandatory_only_overloaded
+    disasm = RubyVM::InstructionSequence.disasm(Time.method(:at))
+    assert_include disasm, "<builtin!time_s_at1/1>"
+    assert_include disasm, "<builtin!time_s_at/4>"
+  end
+
   def strip_lineno(source)
     source.gsub(/^.*?: /, "")
   end
diff --git a/test/test_time.rb b/test/test_time.rb
index 55964d02fc1e78..a4df0b9ef4d9a1 100644
--- a/test/test_time.rb
+++ b/test/test_time.rb
@@ -370,6 +370,15 @@ def test_parse_offset_hour_minute_second
     assert_equal(t, Time.parse("1200-02-15 BC 14:13:20-00:00:00"))
   end
 
+  def test_parse_custom_offset
+    t = Time.at(-100000000000).utc
+    assert_equal(t, Time.parse("1200-02-15 BC 14:13:20", zone: "UTC"))
+    assert_equal(t, Time.parse("1200-02-15 BC 15:13:20", zone: "+01:00").utc)
+
+    assert_equal(t, Time.parse("1200-02-15 BC 15:13:20+01:00", zone: "UTC").utc)
+    assert_equal(t, Time.parse("1200-02-15 BC 15:13:20+01:00", zone: "+02:00").utc)
+  end
+
   def test_parse_leap_second
     t = Time.utc(1998,12,31,23,59,59)
     assert_equal(t, Time.parse("Thu Dec 31 23:59:59 UTC 1998"))
@@ -574,6 +583,7 @@ def test_huge_precision
     test = $1
     define_method(test) {__send__(sub, :xmlschema)}
     define_method(test.sub(/xmlschema/, 'iso8601')) {__send__(sub, :iso8601)}
+    define_method(test.sub(/xmlschema/, 'rfc3339')) {__send__(sub, :rfc3339)}
   end
 
   def test_parse_with_various_object