diff --git a/chrono/datetime.cpp b/chrono/datetime.cpp
index 028f168..92d094c 100644
--- a/chrono/datetime.cpp
+++ b/chrono/datetime.cpp
@@ -78,39 +78,14 @@ DateTime DateTime::fromTimeStamp(time_t timeStamp)
  */
 DateTime DateTime::fromString(const char *str)
 {
-    int values[7] = { 0 };
-    int *const dayIndex = values + 2;
-    int *const secondsIndex = values + 5;
-    int *valueIndex = values;
-    int *const valuesEnd = values + 7;
-    double millisecondsFact = 100.0, milliseconds = 0.0;
-    for (const char *strIndex = str;; ++strIndex) {
-        const char c = *strIndex;
-        if (c <= '9' && c >= '0') {
-            if (valueIndex > secondsIndex) {
-                milliseconds += (c - '0') * millisecondsFact;
-                millisecondsFact /= 10;
-            } else {
-                Detail::raiseAndAdd(*valueIndex, 10, c);
-            }
-        } else if ((c == '-' || c == ':' || c == '/') || (c == '.' && (valueIndex == secondsIndex))
-            || ((c == ' ' || c == 'T') && (valueIndex == dayIndex))) {
-            if (++valueIndex == valuesEnd) {
-                break; // just ignore further values for now
-            }
-        } else if (c == '\0') {
-            break;
-        } else {
-            throw ConversionException(argsToString("Unexpected character \"", c, '\"'));
-        }
-    }
-    return DateTime::fromDateAndTime(values[0], values[1], *dayIndex, values[3], values[4], *secondsIndex, milliseconds);
+    return DateTimeExpression::fromString(str).value;
 }
 
 /*!
  * \brief Parses the specified ISO date time denotation provided as C-style string.
  * \returns Returns a pair where the first value is the parsed date time and the second value
  *          the time zone designator (a time span which can be subtracted from the first value to get the UTC time).
+ * \throws Throws a ConversionException if the specified \a str does not match the expected time format.
  * \remarks
  * - Parsing durations and time intervals is *not* supported.
  * - Truncated representations are *not* supported.
@@ -119,90 +94,8 @@ DateTime DateTime::fromString(const char *str)
  */
 std::pair<DateTime, TimeSpan> DateTime::fromIsoString(const char *str)
 {
-    int values[9] = { 0 };
-    int *const yearIndex = values + 0;
-    int *const monthIndex = values + 1;
-    int *const dayIndex = values + 2;
-    int *const hourIndex = values + 3;
-    int *const secondsIndex = values + 5;
-    int *const miliSecondsIndex = values + 6;
-    int *const deltaHourIndex = values + 7;
-    int *const valuesEnd = values + 9;
-    int *valueIndex = values;
-    unsigned int remainingDigits = 4;
-    bool deltaNegative = false;
-    double millisecondsFact = 100.0, milliseconds = 0.0;
-    for (const char *strIndex = str;; ++strIndex) {
-        const char c = *strIndex;
-        if (c <= '9' && c >= '0') {
-            if (valueIndex == miliSecondsIndex) {
-                milliseconds += (c - '0') * millisecondsFact;
-                millisecondsFact /= 10;
-            } else {
-                if (!remainingDigits) {
-                    if (++valueIndex == miliSecondsIndex || valueIndex >= valuesEnd) {
-                        throw ConversionException("Max. number of digits exceeded");
-                    }
-                    remainingDigits = 2;
-                }
-                *valueIndex *= 10;
-                *valueIndex += c - '0';
-                remainingDigits -= 1;
-            }
-        } else if (c == 'T') {
-            if (++valueIndex != hourIndex) {
-                throw ConversionException("\"T\" expected before hour");
-            }
-            remainingDigits = 2;
-        } else if (c == '-') {
-            if (valueIndex < dayIndex) {
-                ++valueIndex;
-            } else if (++valueIndex >= secondsIndex) {
-                valueIndex = deltaHourIndex;
-                deltaNegative = true;
-            } else {
-                throw ConversionException("Unexpected \"-\" after day");
-            }
-            remainingDigits = 2;
-        } else if (c == '.') {
-            if (valueIndex != secondsIndex) {
-                throw ConversionException("Unexpected \".\"");
-            } else {
-                ++valueIndex;
-            }
-        } else if (c == ':') {
-            if (valueIndex < hourIndex) {
-                throw ConversionException("Unexpected \":\" before hour");
-            } else if (valueIndex == secondsIndex) {
-                throw ConversionException("Unexpected \":\" after second");
-            } else {
-                ++valueIndex;
-            }
-            remainingDigits = 2;
-        } else if ((c == '+') && (++valueIndex >= secondsIndex)) {
-            valueIndex = deltaHourIndex;
-            deltaNegative = false;
-            remainingDigits = 2;
-        } else if ((c == 'Z') && (++valueIndex >= secondsIndex)) {
-            valueIndex = deltaHourIndex + 2;
-            remainingDigits = 2;
-        } else if (c == '\0') {
-            break;
-        } else {
-            throw ConversionException(argsToString("Unexpected \"", c, '\"'));
-        }
-    }
-    auto delta = TimeSpan::fromMinutes(*deltaHourIndex * 60 + values[8]);
-    if (deltaNegative) {
-        delta = TimeSpan(-delta.totalTicks());
-    }
-    if (valueIndex < monthIndex && !*monthIndex) {
-        *monthIndex = 1;
-    }
-    if (valueIndex < dayIndex && !*dayIndex) {
-        *dayIndex = 1;
-    }
-    return make_pair(DateTime::fromDateAndTime(*yearIndex, *monthIndex, *dayIndex, *hourIndex, values[4], *secondsIndex, milliseconds), delta);
+    const auto expr = DateTimeExpression::fromIsoString(str);
+    return std::make_pair(expr.value, expr.delta);
 }
 
 /*!
@@ -466,4 +359,161 @@ int DateTime::getDatePart(DatePart part) const
     return 0;
 }
 
+/// \cond
+static DateTimeParts dateTimePartsFromParsingDistance(const int *valueIndex, const int *values)
+{
+    return static_cast<DateTimeParts>((1 << (valueIndex - values + 1)) - 1);
+}
+/// \endcond
+
+/*!
+ * \brief Parses the specified ISO date time denotation provided as C-style string.
+ * \throws Throws a ConversionException if the specified \a str does not match the expected time format.
+ * \remarks
+ * - Parsing durations and time intervals is *not* supported.
+ * - Truncated representations are *not* supported.
+ * - Standardised extensions (ISO 8601-2:2019) are *not* supported.
+ * \sa https://en.wikipedia.org/wiki/ISO_8601
+ */
+DateTimeExpression DateTimeExpression::fromIsoString(const char *str)
+{
+    auto res = DateTimeExpression();
+    int values[9] = { 0 };
+    int *const yearIndex = values + 0;
+    int *const monthIndex = values + 1;
+    int *const dayIndex = values + 2;
+    int *const hourIndex = values + 3;
+    int *const secondsIndex = values + 5;
+    int *const miliSecondsIndex = values + 6;
+    int *const deltaHourIndex = values + 7;
+    int *const valuesEnd = values + 9;
+    int *valueIndex = values;
+    unsigned int remainingDigits = 4;
+    bool deltaNegative = false;
+    double millisecondsFact = 100.0, milliseconds = 0.0;
+    for (const char *strIndex = str;; ++strIndex) {
+        const char c = *strIndex;
+        if (c <= '9' && c >= '0') {
+            if (valueIndex == miliSecondsIndex) {
+                milliseconds += (c - '0') * millisecondsFact;
+                millisecondsFact /= 10;
+            } else {
+                if (!remainingDigits) {
+                    if (++valueIndex == miliSecondsIndex || valueIndex >= valuesEnd) {
+                        throw ConversionException("Max. number of digits exceeded");
+                    }
+                    remainingDigits = 2;
+                }
+                *valueIndex *= 10;
+                *valueIndex += c - '0';
+                remainingDigits -= 1;
+            }
+        } else if (c == 'T') {
+            if (++valueIndex != hourIndex) {
+                throw ConversionException("\"T\" expected before hour");
+            }
+            remainingDigits = 2;
+        } else if (c == '-') {
+            if (valueIndex < dayIndex) {
+                ++valueIndex;
+            } else if (++valueIndex >= secondsIndex) {
+                valueIndex = deltaHourIndex;
+                deltaNegative = true;
+            } else {
+                throw ConversionException("Unexpected \"-\" after day");
+            }
+            remainingDigits = 2;
+        } else if (c == '.') {
+            if (valueIndex != secondsIndex) {
+                throw ConversionException("Unexpected \".\"");
+            } else {
+                ++valueIndex;
+            }
+        } else if (c == ':') {
+            if (valueIndex < hourIndex) {
+                throw ConversionException("Unexpected \":\" before hour");
+            } else if (valueIndex == secondsIndex) {
+                throw ConversionException("Unexpected \":\" after second");
+            } else {
+                ++valueIndex;
+            }
+            remainingDigits = 2;
+        } else if ((c == '+') && (++valueIndex >= secondsIndex)) {
+            valueIndex = deltaHourIndex;
+            deltaNegative = false;
+            remainingDigits = 2;
+        } else if ((c == 'Z') && (++valueIndex >= secondsIndex)) {
+            valueIndex = deltaHourIndex + 2;
+            remainingDigits = 2;
+        } else if (c == '\0') {
+            break;
+        } else {
+            throw ConversionException(argsToString("Unexpected \"", c, '\"'));
+        }
+    }
+    res.delta = TimeSpan::fromMinutes(*deltaHourIndex * 60 + values[8]);
+    if (deltaNegative) {
+        res.delta = TimeSpan(-res.delta.totalTicks());
+    }
+    if (valueIndex < monthIndex && !*monthIndex) {
+        *monthIndex = 1;
+    }
+    if (valueIndex < dayIndex && !*dayIndex) {
+        *dayIndex = 1;
+    }
+    res.value = DateTime::fromDateAndTime(*yearIndex, *monthIndex, *dayIndex, *hourIndex, values[4], *secondsIndex, milliseconds);
+    res.parts = dateTimePartsFromParsingDistance(valueIndex, values);
+    return res;
+}
+
+/*!
+ * \brief Parses the given C-style string.
+ * \throws Throws a ConversionException if the specified \a str does not match the expected time format.
+ *
+ * The expected format is something like "2012-02-29 15:34:20.033" or "2012/02/29 15:34:20.033". The
+ * delimiters '-', ':' and '/' are exchangeable.
+ *
+ * \sa DateTimeExpression::fromIsoString()
+ */
+DateTimeExpression DateTimeExpression::fromString(const char *str)
+{
+    auto res = DateTimeExpression();
+    int values[7] = { 0 };
+    int *const monthIndex = values + 1;
+    int *const dayIndex = values + 2;
+    int *const secondsIndex = values + 5;
+    int *valueIndex = values;
+    int *const valuesEnd = values + 7;
+    double millisecondsFact = 100.0, milliseconds = 0.0;
+    for (const char *strIndex = str;; ++strIndex) {
+        const char c = *strIndex;
+        if (c <= '9' && c >= '0') {
+            if (valueIndex > secondsIndex) {
+                milliseconds += (c - '0') * millisecondsFact;
+                millisecondsFact /= 10;
+            } else {
+                Detail::raiseAndAdd(*valueIndex, 10, c);
+            }
+        } else if ((c == '-' || c == ':' || c == '/') || (c == '.' && (valueIndex == secondsIndex))
+            || ((c == ' ' || c == 'T') && (valueIndex == dayIndex))) {
+            if (++valueIndex == valuesEnd) {
+                break; // just ignore further values for now
+            }
+        } else if (c == '\0') {
+            break;
+        } else {
+            throw ConversionException(argsToString("Unexpected character \"", c, '\"'));
+        }
+    }
+    if (valueIndex < monthIndex && !*monthIndex) {
+        *monthIndex = 1;
+    }
+    if (valueIndex < dayIndex && !*dayIndex) {
+        *dayIndex = 1;
+    }
+    res.value = DateTime::fromDateAndTime(values[0], values[1], *dayIndex, values[3], values[4], *secondsIndex, milliseconds);
+    res.parts = dateTimePartsFromParsingDistance(valueIndex, values);
+    return res;
+}
+
 } // namespace CppUtilities
diff --git a/chrono/datetime.h b/chrono/datetime.h
index f62a792..6cee87f 100644
--- a/chrono/datetime.h
+++ b/chrono/datetime.h
@@ -3,6 +3,8 @@
 
 #include "./timespan.h"
 
+#include "../misc/flagenumclass.h"
+
 #include <cstdint>
 #include <ctime>
 #include <limits>
@@ -137,6 +139,43 @@ private:
     static const int m_daysInMonth366[12];
 };
 
+/*!
+ * \brief The DateTimeParts enum specifies which parts of a timestamp are present.
+ */
+enum class DateTimeParts : std::uint64_t {
+    None = 0, /**< no parts are present */
+    Year = (1 << 0), /**< the year is present */
+    Month = (1 << 1), /**< the month is present */
+    Day = (1 << 2), /**< the day is present */
+    Hour = (1 << 3), /**< the hour is present */
+    Minute = (1 << 4), /**< the minute is present */
+    Second = (1 << 5), /**< the second is present */
+    Millisecond = (1 << 6), /**< the millisecond is present */
+    DeltaHour = (1 << 7), /**< the timezone-delta hour is present */
+    DeltaMinute = (1 << 8), /**< the timezone-delta minute is present */
+};
+
+/*!
+ * \brief The DateTimeExpression struct holds information about a time expression (e.g. an ISO-8601 timestamp).
+ */
+struct CPP_UTILITIES_EXPORT DateTimeExpression {
+    DateTime value; /**< The value of the time expression as DateTime object. */
+    TimeSpan delta; /**< The delta of \a value from UTC as TimeSpan object. */
+    DateTimeParts parts = DateTimeParts::None; /**< The parts present in the expression as flag enum. */
+
+    constexpr DateTime gmt() const;
+    static DateTimeExpression fromIsoString(const char *str);
+    static DateTimeExpression fromString(const char *str);
+};
+
+/*!
+ * \brief Returns the value in UTC time.
+ */
+constexpr DateTime DateTimeExpression::gmt() const
+{
+    return value - delta;
+}
+
 /*!
  * \brief Constructs a DateTime.
  */
@@ -203,8 +242,7 @@ inline DateTime DateTime::fromString(const std::string &str)
  */
 inline DateTime DateTime::fromIsoStringGmt(const char *str)
 {
-    const auto tmp = fromIsoString(str);
-    return tmp.first - tmp.second;
+    return DateTimeExpression::fromIsoString(str).gmt();
 }
 
 /*!
@@ -215,7 +253,7 @@ inline DateTime DateTime::fromIsoStringGmt(const char *str)
  */
 inline DateTime DateTime::fromIsoStringLocal(const char *str)
 {
-    return fromIsoString(str).first;
+    return DateTimeExpression::fromIsoString(str).value;
 }
 
 /*!
@@ -579,4 +617,6 @@ template <> struct hash<CppUtilities::DateTime> {
 };
 } // namespace std
 
+CPP_UTILITIES_MARK_FLAG_ENUM_CLASS(CppUtilities, CppUtilities::DateTimeParts);
+
 #endif // CHRONO_UTILITIES_DATETIME_H
diff --git a/tests/chronotests.cpp b/tests/chronotests.cpp
index f608928..a826bd1 100644
--- a/tests/chronotests.cpp
+++ b/tests/chronotests.cpp
@@ -70,6 +70,7 @@ static_assert(TimeSpan::fromDays(20.5).totalDays() == 20.5, "totalDays()");
 class ChronoTests : public TestFixture {
     CPPUNIT_TEST_SUITE(ChronoTests);
     CPPUNIT_TEST(testDateTime);
+    CPPUNIT_TEST(testDateTimeExpression);
     CPPUNIT_TEST(testTimeSpan);
     CPPUNIT_TEST(testOperators);
     CPPUNIT_TEST(testPeriod);
@@ -85,6 +86,7 @@ public:
     }
 
     void testDateTime();
+    void testDateTimeExpression();
     void testTimeSpan();
     void testOperators();
     void testPeriod();
@@ -223,6 +225,84 @@ void ChronoTests::testDateTime()
 #endif
 }
 
+/*!
+ * \brief Tests parsing a DateTimeExpression. Checks for the parts in particular.
+ */
+void ChronoTests::testDateTimeExpression()
+{
+    // check adding ISO timestamp parts one-by-one
+    auto expr = DateTimeExpression::fromIsoString("1");
+    auto parts = DateTimeParts::Year;
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts, expr.parts);
+    expr = DateTimeExpression::fromIsoString("1-1");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Month, expr.parts);
+    expr = DateTimeExpression::fromIsoString("1-1-1");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Day, expr.parts);
+    expr = DateTimeExpression::fromIsoString("1-1-1T0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Hour, expr.parts);
+    expr = DateTimeExpression::fromIsoString("1-1-1T0:0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Minute, expr.parts);
+    expr = DateTimeExpression::fromIsoString("1-1-1T0:0:0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Second, expr.parts);
+    expr = DateTimeExpression::fromIsoString("1-1-1T0:0:0.0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Millisecond, expr.parts);
+    expr = DateTimeExpression::fromIsoString("1-1-1T0:0:0.0+0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::DeltaHour, expr.parts);
+    expr = DateTimeExpression::fromIsoString("1-1-1T0:0:0.0-0:0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::DeltaMinute, expr.parts);
+
+    // check that omitting parts in the middle is not possible anyways
+    CPPUNIT_ASSERT_THROW(DateTimeExpression::fromIsoString("1-1T0"), ConversionException);
+
+    // check ::fromString()
+    expr = DateTimeExpression::fromString("1");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts = DateTimeParts::Year, expr.parts);
+    expr = DateTimeExpression::fromString("1/1");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Month, expr.parts);
+    expr = DateTimeExpression::fromString("1/1/1");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Day, expr.parts);
+    expr = DateTimeExpression::fromString("1/1/1 0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Hour, expr.parts);
+    expr = DateTimeExpression::fromString("1/1/1 0:0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Minute, expr.parts);
+    expr = DateTimeExpression::fromString("1/1/1 0:0:0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Second, expr.parts);
+    expr = DateTimeExpression::fromString("1/1/1 0:0:0.0");
+    CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
+    CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Millisecond, expr.parts);
+}
+
 /*!
  * \brief Tests most important TimeSpan features.
  */