diff --git a/caddyhttp/httpserver/replacer.go b/caddyhttp/httpserver/replacer.go
index b112e8354..0278eb510 100644
--- a/caddyhttp/httpserver/replacer.go
+++ b/caddyhttp/httpserver/replacer.go
@@ -23,6 +23,8 @@ var requestReplacer = strings.NewReplacer(
 	"\n", "\\n",
 )
 
+var now = time.Now
+
 // Replacer is a type which can replace placeholder
 // substrings in a string with actual values from a
 // http.Request and ResponseRecorder. Always use
@@ -249,7 +251,9 @@ func (r *replacer) getSubstitution(key string) string {
 	case "{uri_escaped}":
 		return url.QueryEscape(r.request.URL.RequestURI())
 	case "{when}":
-		return time.Now().Format(timeFormat)
+		return now().Format(timeFormat)
+	case "{when_iso}":
+		return now().UTC().Format(timeFormatISOUTC)
 	case "{file}":
 		_, file := path.Split(r.request.URL.Path)
 		return file
@@ -311,6 +315,7 @@ func (r *replacer) Set(key, value string) {
 
 const (
 	timeFormat        = "02/Jan/2006:15:04:05 -0700"
+	timeFormatISOUTC  = "2006-01-02T15:04:05Z" // ISO 8601 with timezone to be assumed as UTC
 	headerContentType = "Content-Type"
 	contentTypeJSON   = "application/json"
 	contentTypeXML    = "application/xml"
diff --git a/caddyhttp/httpserver/replacer_test.go b/caddyhttp/httpserver/replacer_test.go
index fb5535496..e03aed81c 100644
--- a/caddyhttp/httpserver/replacer_test.go
+++ b/caddyhttp/httpserver/replacer_test.go
@@ -53,6 +53,13 @@ func TestReplace(t *testing.T) {
 		t.Fatal("Failed to determine hostname\n")
 	}
 
+	old := now
+	now = func() time.Time {
+		return time.Date(2006, 1, 2, 15, 4, 5, 02, time.FixedZone("hardcoded", -7))
+	}
+	defer func() {
+		now = old
+	}()
 	testCases := []struct {
 		template string
 		expect   string
@@ -61,6 +68,8 @@ func TestReplace(t *testing.T) {
 		{"This host is {host}.", "This host is localhost."},
 		{"This request method is {method}.", "This request method is POST."},
 		{"The response status is {status}.", "The response status is 200."},
+		{"{when}", "02/Jan/2006:15:04:05 +0000"},
+		{"{when_iso}", "2006-01-02T15:04:12Z"},
 		{"The Custom header is {>Custom}.", "The Custom header is foobarbaz."},
 		{"The CustomAdd header is {>CustomAdd}.", "The CustomAdd header is caddy."},
 		{"The request is {request}.", "The request is POST / HTTP/1.1\\r\\nHost: localhost\\r\\nCustom: foobarbaz\\r\\nCustomadd: caddy\\r\\nShorterval: 1\\r\\n\\r\\n."},