diff --git a/tools/nfdc/format-helpers.cpp b/tools/nfdc/format-helpers.cpp
index fa72512..a207bf8 100644
--- a/tools/nfdc/format-helpers.cpp
+++ b/tools/nfdc/format-helpers.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2018,  Regents of the University of California,
+ * Copyright (c) 2014-2021,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -110,9 +110,9 @@
 }
 
 std::string
-formatTimestamp(time::system_clock::TimePoint t)
+formatTimestamp(time::system_clock::time_point t)
 {
-  return time::toString(t, "%Y-%m-%dT%H:%M:%S%F");
+  return time::toIsoExtendedString(t);
 }
 
 } // namespace xml
@@ -199,7 +199,7 @@
 }
 
 std::string
-formatTimestamp(time::system_clock::TimePoint t)
+formatTimestamp(time::system_clock::time_point t)
 {
   return time::toIsoString(t);
 }