Refine QCalendar::hasYearZero()'s documentation

Change-Id: I06697485c6be1c31998d0da54b357f3f5c8701e7
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

src/corelib/time/qcalendar.cpp

@@ -837,29 +837,29 @@ bool QCalendar::isProleptic() const
 }
 
 /*!
-  Returns \c true if this calendar has a year zero.
+    Returns \c true if this calendar has a year zero.
 
-  A non-proleptic calendar with no year zero represents years from its first
+    A calendar may represent years from its first year onwards but provide no
-  year onwards but provides no way to describe years before its first; such a
+    way to describe years before its first; such a calendar has no year zero and
-  calendar has no year zero and is not proleptic.
+    is not proleptic.
 
-  A calendar which represents years before its first may number these years
+    A calendar which represents years before its first may number these years
-  simply by following the usual integer counting, so that the year before the
+    simply by following the usual integer counting, so that the year before the
-  first is year zero, with negative-numbered years preceding this; such a
+    first is year zero, with negative-numbered years preceding this; such a
-  calendar is proleptic and has a year zero. A calendar might also have a year
+    calendar is proleptic and has a year zero. A calendar might also have a year
-  zero (for example, the year of some great event, with subsequent years being
+    zero (for example, the year of some great event, with subsequent years being
-  the first year after that event, the second year after, and so on) without
+    the first year after that event, the second year after, and so on) without
-  describing years before its year zero. Such a calendar would have a year zero
+    describing years before its year zero. Such a calendar would have a year
-  without being proleptic.
+    zero without being proleptic.
 
-  Some calendars, however, represent years before their first by an alternate
+    Some calendars, however, represent years before their first by an alternate
-  numbering; for example, the proleptic Gregorian calendar's first year is 1 CE
+    numbering; for example, the proleptic Gregorian calendar's first year is 1
-  and the year before it is 1 BCE, preceded by 2 BCE and so on. In this case,
+    CE and the year before it is 1 BCE, preceded by 2 BCE and so on. In this
-  we use negative year numbers, with year -1 as the year before year 1, year -2
+    case, we use negative year numbers for this alternate numbering, with year
-  as the year before year -1 and so on. Such a calendar is proleptic but has no
+    -1 as the year before year 1, year -2 as the year before year -1 and so
-  year zero.
+    on. Such a calendar is proleptic but has no year zero.
 
-  \sa isProleptic()
+    \sa isProleptic()
 */
 bool QCalendar::hasYearZero() const
 {