diff --git a/exercises/practice/gigasecond/.meta/example.lua b/exercises/practice/gigasecond/.meta/example.lua
index d0da648..6eaeb9b 100644
--- a/exercises/practice/gigasecond/.meta/example.lua
+++ b/exercises/practice/gigasecond/.meta/example.lua
@@ -3,7 +3,7 @@
 local gigasecond = {}
 
 function gigasecond.anniversary(any_date)
-  return os.date('%x', any_date + math.pow(10, 9))
+  return os.date('!%x', any_date + math.pow(10, 9))
 end
 
 return gigasecond
diff --git a/exercises/practice/gigasecond/.meta/spec_generator.lua b/exercises/practice/gigasecond/.meta/spec_generator.lua
new file mode 100644
index 0000000..9f5a6c6
--- /dev/null
+++ b/exercises/practice/gigasecond/.meta/spec_generator.lua
@@ -0,0 +1,33 @@
+local function components(moment)
+  return moment:match("(%d%d%d%d)%-(%d%d)%-(%d%d)T?(%d*):?(%d*):?(%d*)")
+end
+
+local function map_to_num(...)
+  local t = { ... }
+  for i, str in ipairs(t) do
+    if str ~= nil and str ~= '' then
+      t[i] = tonumber(str)
+    else
+      t[i] = 0
+    end
+  end
+  return table.unpack(t)
+end
+
+return {
+  module_name = 'gigasecond',
+
+  generate_test = function(case)
+    local year, month, day, hour, min, sec = map_to_num(components(case.input.moment))
+    local e_year, e_month, e_day, e_hour, e_min, e_sec = map_to_num(components(case.expected))
+
+    local template = [[
+      local moment_a = os.time({ year = %d, month = %d, day = %d, hour = %d, min = %d, sec = %d })
+      local moment_b = os.time({ year = %d, month = %d, day = %d, hour = %d, min = %d, sec = %d })
+      local actual = gigasecond.anniversary(moment_a)
+      local expected = os.date('!%%x', moment_b)
+      assert.are.equals(expected, actual)]]
+
+    return template:format(year, month, day, hour, min, sec, e_year, e_month, e_day, e_hour, e_min, e_sec)
+  end
+}
diff --git a/exercises/practice/gigasecond/gigasecond_spec.lua b/exercises/practice/gigasecond/gigasecond_spec.lua
index d5d12e1..eb33149 100644
--- a/exercises/practice/gigasecond/gigasecond_spec.lua
+++ b/exercises/practice/gigasecond/gigasecond_spec.lua
@@ -1,27 +1,43 @@
 local gigasecond = require('gigasecond')
 
 describe('gigasecond', function()
-  it('test 1', function()
-    local actual = gigasecond.anniversary(os.time({ year = 2011, month = 3, day = 25, hour = 0, min = 0, sec = 0 }))
-    local expectedDate = os.date('%x', os.time({ year = 2042, month = 12, day = 1, hour = 0, min = 0, sec = 0 }))
-    assert.are.equals(expectedDate, actual)
+  it('date only specification of time', function()
+    local moment_a = os.time({ year = 2011, month = 4, day = 25, hour = 0, min = 0, sec = 0 })
+    local moment_b = os.time({ year = 2043, month = 1, day = 1, hour = 1, min = 46, sec = 40 })
+    local actual = gigasecond.anniversary(moment_a)
+    local expected = os.date('!%x', moment_b)
+    assert.are.equals(expected, actual)
   end)
 
-  it('test 2', function()
-    local actual = gigasecond.anniversary(os.time({ year = 1977, month = 5, day = 13, hour = 0, min = 0, sec = 0 }))
-    local expectedDate = os.date('%x', os.time({ year = 2009, month = 1, day = 19 }))
-    assert.are.equals(expectedDate, actual)
+  it('second test for date only specification of time', function()
+    local moment_a = os.time({ year = 1977, month = 6, day = 13, hour = 0, min = 0, sec = 0 })
+    local moment_b = os.time({ year = 2009, month = 2, day = 19, hour = 1, min = 46, sec = 40 })
+    local actual = gigasecond.anniversary(moment_a)
+    local expected = os.date('!%x', moment_b)
+    assert.are.equals(expected, actual)
   end)
 
-  it('test 3', function()
-    local actual = gigasecond.anniversary(os.time({ year = 1999, month = 7, day = 19 }))
-    local expectedDate = os.date('%x', os.time({ year = 2031, month = 3, day = 27 }))
-    assert.are.equals(expectedDate, actual)
+  it('third test for date only specification of time', function()
+    local moment_a = os.time({ year = 1959, month = 7, day = 19, hour = 0, min = 0, sec = 0 })
+    local moment_b = os.time({ year = 1991, month = 3, day = 27, hour = 1, min = 46, sec = 40 })
+    local actual = gigasecond.anniversary(moment_a)
+    local expected = os.date('!%x', moment_b)
+    assert.are.equals(expected, actual)
   end)
 
-  it('test 4', function()
-    local actual = gigasecond.anniversary(os.time({ year = 1993, month = 8, day = 17 }))
-    local expectedDate = os.date('%x', os.time({ year = 2025, month = 4, day = 25 }))
-    assert.are.equals(expectedDate, actual)
+  it('full time specified', function()
+    local moment_a = os.time({ year = 2015, month = 1, day = 24, hour = 22, min = 0, sec = 0 })
+    local moment_b = os.time({ year = 2046, month = 10, day = 2, hour = 23, min = 46, sec = 40 })
+    local actual = gigasecond.anniversary(moment_a)
+    local expected = os.date('!%x', moment_b)
+    assert.are.equals(expected, actual)
+  end)
+
+  it('full time with day roll-over', function()
+    local moment_a = os.time({ year = 2015, month = 1, day = 24, hour = 23, min = 59, sec = 59 })
+    local moment_b = os.time({ year = 2046, month = 10, day = 3, hour = 1, min = 46, sec = 39 })
+    local actual = gigasecond.anniversary(moment_a)
+    local expected = os.date('!%x', moment_b)
+    assert.are.equals(expected, actual)
   end)
 end)