github
diff --git a/‎test/ruby/test_time_tz.rb
Lines changed: 2 additions & 2 deletions b/‎test/ruby/test_time_tz.rb
Lines changed: 2 additions & 2 deletions
diff --git a/‎time.c
Lines changed: 12 additions & 6 deletions b/‎time.c
Lines changed: 12 additions & 6 deletions
@@ -547,11 +547,11 @@ def subtest_plus(time_class, tz, tzarg, tzname, abbr, utc_offset)
   def subtest_at(time_class, tz, tzarg, tzname, abbr, utc_offset)
     h, m = (utc_offset / 60).divmod(60)
     utc = time_class.utc(2018, 9, 1, 12, 0, 0)
-    t = time_class.at(utc, tzarg)
+    t = time_class.at(utc, in: tzarg)
     assert_equal([2018, 9, 1, 12+h, m, 0, tz], [t.year, t.mon, t.mday, t.hour, t.min, t.sec, t.zone])
     assert_equal(utc.to_i, t.to_i)
     utc = utc.to_i
-    t = time_class.at(utc, tzarg)
+    t = time_class.at(utc, in: tzarg)
     assert_equal([2018, 9, 1, 12+h, m, 0, tz], [t.year, t.mon, t.mday, t.hour, t.min, t.sec, t.zone])
     assert_equal(utc, t.to_i)
   end
 
@@ -2686,7 +2686,7 @@ get_scale(VALUE unit)
  *  can be an Integer, Float, Rational, or other Numeric.
  *  non-portable feature allows the offset to be negative on some systems.
  *
- *  If +tz+ argument is given, the result is in that timezone or UTC offset, or
+ *  If +in+ argument is given, the result is in that timezone or UTC offset, or
  *  if a numeric argument is given, the result is in local time.
  *
  *     Time.at(0)                                #=> 1969-12-31 18:00:00 -0600
@@ -2701,13 +2701,19 @@ get_scale(VALUE unit)
 static VALUE
 time_s_at(int argc, VALUE *argv, VALUE klass)
 {
-    VALUE time, t, unit = Qundef, zone = Qnil;
+    VALUE time, t, unit = Qundef, zone = Qundef, opts;
     wideval_t timew;
 
-    if (argc > 1 && rb_obj_respond_to(argv[argc-1], id_utc_to_local, Qfalse)) {
-        zone = argv[--argc];
+    argc = rb_scan_args(argc, argv, "12:", &time, &t, &unit, &opts);
+    if (!NIL_P(opts)) {
+        ID ids[1];
+        VALUE vals[numberof(ids)];
+
+        CONST_ID(ids[0], "in");
+        rb_get_kwargs(opts, ids, 0, 1, vals);
+        zone = vals[0];
     }
-    if (rb_scan_args(argc, argv, "12", &time, &t, &unit) >= 2) {
+    if (argc >= 2) {
         int scale = argc == 3 ? get_scale(unit) : 1000000;
         time = num_exact(time);
         t = num_exact(t);
@@ -2725,7 +2731,7 @@ time_s_at(int argc, VALUE *argv, VALUE klass)
         timew = rb_time_magnify(v2w(num_exact(time)));
         t = time_new_timew(klass, timew);
     }
-    if (!NIL_P(zone)) {
+    if (zone != Qundef) {
         time_zonelocal(t, zone);
     }