Improve docs for `DateTimeExpression`

chrono/datetime.cpp

@@ -53,6 +53,18 @@ template <typename num1, typename num2, typename num3> constexpr bool inRangeExc
  *   invocations of getDatePart().
  */
 
+/*!
+ * \struct DateTimeExpression
+ * \brief The DateTimeExpression struct holds information about a time expression (e.g. an ISO-8601 timestamp).
+ *
+ * This struct holds the date and time specification (DateTimeExpression::value), the time-zone delta
+ * (DateTimeExpression::delta) and what parts are actually specified (DateTimeExpression::parts).
+ *
+ * The idea is to be able to preserve a time-zone delta and present parts when deserializing and then
+ * serializing again. Note that it still does not allow to preserve the format of the original timestamp
+ * exactly.
+ */
+
 /*!
  * \brief Constructs a new DateTime object with the local time from the specified UNIX \a timeStamp.
  */

chrono/datetime.h

@@ -155,9 +155,6 @@ enum class DateTimeParts : std::uint64_t {
     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. */