diff --git a/synautil.pas b/synautil.pas
index 54b2f9c..dd34aee 100644
--- a/synautil.pas
+++ b/synautil.pas
@@ -1,9 +1,9 @@
 {==============================================================================|
-| Project : Ararat Synapse                                       | 004.015.007 |
+| Project : Ararat Synapse                                       | 004.016.000 |
 |==============================================================================|
 | Content: support procedures and functions                                    |
 |==============================================================================|
-| Copyright (c)1999-2017, Lukas Gebauer                                        |
+| Copyright (c)1999-2023, Lukas Gebauer                                        |
 | All rights reserved.                                                         |
 |                                                                              |
 | Redistribution and use in source and binary forms, with or without           |
@@ -33,7 +33,7 @@
 | DAMAGE.                                                                      |
 |==============================================================================|
 | The Initial Developer of the Original Code is Lukas Gebauer (Czech Republic).|
-| Portions created by Lukas Gebauer are Copyright (c) 1999-2017.               |
+| Portions created by Lukas Gebauer are Copyright (c) 1999-2023.               |
 | Portions created by Hernan Sanchez are Copyright (c) 2000.                   |
 | Portions created by Petr Fejfar are Copyright (c)2011-2012.                  |
 | All Rights Reserved.                                                         |
@@ -124,6 +124,9 @@ function TimeZone: string;
  'Fri, 15 Oct 1999 21:14:56 +0200')}
 function Rfc822DateTime(t: TDateTime): string;
 
+{:Returns date and time in format defined in RFC-3339 in format "yyyy-mm-ddThh:nn:ss.zzz"}
+function Rfc3339DateTime(t: TDateTime): string;
+
 {:Returns date and time in format defined in C compilers in format "mmm dd hh:nn:ss"}
 function CDateTime(t: TDateTime): string;
 
@@ -491,6 +494,13 @@ end;
 
 {==============================================================================}
 
+function Rfc3339DateTime(t: TDateTime): string;
+begin
+  Result := FormatDateTime('yyyy"-"mm"-"dd"T"hh":"nn":"ss"."zzz', t) + Timezone;
+end;
+
+{==============================================================================}
+
 function CDateTime(t: TDateTime): string;
 var
   wYear, wMonth, wDay: word;