diff --git a/CMakeLists.txt b/CMakeLists.txt
index 86ac6e1..1527600 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -112,8 +112,8 @@ set(META_APP_URL "https://github.com/${META_APP_AUTHOR}/${META_PROJECT_NAME}")
 set(META_APP_DESCRIPTION "Useful C++ classes and routines such as argument parser, IO and conversion utilities")
 set(META_FEATURES_FOR_COMPILER_DETECTION_HEADER cxx_thread_local)
 set(META_VERSION_MAJOR 5)
-set(META_VERSION_MINOR 3)
-set(META_VERSION_PATCH 1)
+set(META_VERSION_MINOR 4)
+set(META_VERSION_PATCH 0)
 
 # find required 3rd party libraries
 include(3rdParty)
diff --git a/chrono/datetime.cpp b/chrono/datetime.cpp
index eacc289..7dad960 100644
--- a/chrono/datetime.cpp
+++ b/chrono/datetime.cpp
@@ -210,14 +210,14 @@ void DateTime::toString(string &result, DateTimeOutputFormat format, bool noMill
 }
 
 /*!
- * \brief Returns the string representation of the current instance in the ISO format,
- *        eg. 2016-08-29T21:32:31.588539814+02:00.
+ * \brief Returns the string representation of the current instance in the ISO format with custom delimiters,
+ *        eg. 2016/08/29T21-32-31.588539814+02:00 with '/' as \a dateDelimiter and '-' as \a timeDelimiter.
  */
-string DateTime::toIsoString(TimeSpan timeZoneDelta) const
+string DateTime::toIsoStringWithCustomDelimiters(TimeSpan timeZoneDelta, char dateDelimiter, char timeDelimiter, char timeZoneDelimiter) const
 {
     stringstream s(stringstream::in | stringstream::out);
     s << setfill('0');
-    s << setw(4) << year() << '-' << setw(2) << month() << '-' << setw(2) << day() << 'T' << setw(2) << hour() << ':' << setw(2) << minute() << ':'
+    s << setw(4) << year() << dateDelimiter << setw(2) << month() << dateDelimiter << setw(2) << day() << 'T' << setw(2) << hour() << timeDelimiter << setw(2) << minute() << timeDelimiter
       << setw(2) << second();
     const int milli(millisecond());
     const int micro(microsecond());
@@ -238,11 +238,20 @@ string DateTime::toIsoString(TimeSpan timeZoneDelta) const
         } else {
             s << '+';
         }
-        s << setw(2) << timeZoneDelta.hours() << ':' << setw(2) << timeZoneDelta.minutes();
+        s << setw(2) << timeZoneDelta.hours() << timeZoneDelimiter << setw(2) << timeZoneDelta.minutes();
     }
     return s.str();
 }
 
+/*!
+ * \brief Returns the string representation of the current instance in the ISO format,
+ *        eg. 2016-08-29T21:32:31.588539814+02:00.
+ */
+string DateTime::toIsoString(TimeSpan timeZoneDelta) const
+{
+    return toIsoStringWithCustomDelimiters(timeZoneDelta);
+}
+
 /*!
  * \brief Returns the string representation as C-style string for the given day of week.
  *
diff --git a/chrono/datetime.h b/chrono/datetime.h
index 8d252fd..308fdf4 100644
--- a/chrono/datetime.h
+++ b/chrono/datetime.h
@@ -85,6 +85,7 @@ public:
     constexpr bool isSameDay(const DateTime &other) const;
     std::string toString(DateTimeOutputFormat format = DateTimeOutputFormat::DateAndTime, bool noMilliseconds = false) const;
     void toString(std::string &result, DateTimeOutputFormat format = DateTimeOutputFormat::DateAndTime, bool noMilliseconds = false) const;
+    std::string toIsoStringWithCustomDelimiters(TimeSpan timeZoneDelta = TimeSpan(), char dateDelimiter = '-', char timeDelimiter = ':', char timeZoneDelimiter = ':') const;
     std::string toIsoString(TimeSpan timeZoneDelta = TimeSpan()) const;
     constexpr std::time_t toTimeStamp() const;
     static const char *printDayOfWeek(DayOfWeek dayOfWeek, bool abbreviation = false);