Fix editing dates with days sometimes off by one day. Fixes #2042815 [problems with dates](https://bugs.launchpad.net/calibre/+bug/2042815)

The problem seems to be some change in PyQt that causes auto-conversion
of python datetime objects to QDateTime to lose timezone information.
So we convert manually preserving that information.

src/calibre/gui2/__init__.py

@@ -11,7 +11,7 @@ import threading
 from contextlib import contextmanager, suppress
 from functools import lru_cache
 from qt.core import (
-    QApplication, QBuffer, QByteArray, QColor, QDateTime, QDesktopServices, QDialog,
+    QApplication, QBuffer, QByteArray, QColor, QDesktopServices, QDialog,
     QDialogButtonBox, QEvent, QFile, QFileDialog, QFileIconProvider, QFileInfo, QFont,
     QFontDatabase, QFontInfo, QFontMetrics, QGuiApplication, QIcon, QImageReader,
     QImageWriter, QIODevice, QLocale, QNetworkProxyFactory, QObject, QPalette,
@@ -37,7 +37,7 @@ from calibre.gui2.qt_file_dialogs import FileDialog
 from calibre.ptempfile import base_dir
 from calibre.utils.config import Config, ConfigProxy, JSONConfig, dynamic
 from calibre.utils.config_base import tweaks
-from calibre.utils.date import UNDEFINED_DATE
+from calibre.utils.date import UNDEFINED_DATE, qt_from_dt
 from calibre.utils.file_type_icons import EXT_MAP
 from calibre.utils.img import set_image_allocation_limit
 from calibre.utils.localization import get_lang
@@ -428,7 +428,7 @@ create_defs()
 del create_defs
 # }}}
 
-UNDEFINED_QDATETIME = QDateTime(UNDEFINED_DATE)
+UNDEFINED_QDATETIME = qt_from_dt(UNDEFINED_DATE, as_utc=True)
 QT_HIDDEN_CLEAR_ACTION = '_q_qlineeditclearaction'
 ALL_COLUMNS = ['title', 'ondevice', 'authors', 'size', 'timestamp', 'rating', 'publisher',
         'tags', 'series', 'pubdate']

src/calibre/gui2/custom_column_widgets.py

@@ -9,7 +9,7 @@ import os
 from collections import OrderedDict
 from functools import partial
 from qt.core import (
-    QApplication, QCheckBox, QComboBox, QDateTime, QDialog, QDoubleSpinBox, QGridLayout,
+    QApplication, QCheckBox, QComboBox, QDialog, QDoubleSpinBox, QGridLayout,
     QGroupBox, QHBoxLayout, QIcon, QLabel, QLineEdit, QMessageBox, QPlainTextEdit,
     QSizePolicy, QSpacerItem, QSpinBox, QStyle, Qt, QToolButton, QUrl, QVBoxLayout,
     QWidget,
@@ -18,15 +18,16 @@ from qt.core import (
 from calibre.ebooks.metadata import title_sort
 from calibre.gui2 import UNDEFINED_QDATETIME, elided_text, error_dialog, gprefs
 from calibre.gui2.comments_editor import Editor as CommentsEditor
-from calibre.gui2.markdown_editor import Editor as MarkdownEditor
 from calibre.gui2.complete2 import EditWithComplete as EWC
 from calibre.gui2.dialogs.tag_editor import TagEditor
 from calibre.gui2.library.delegates import ClearingDoubleSpinBox, ClearingSpinBox
+from calibre.gui2.markdown_editor import Editor as MarkdownEditor
 from calibre.gui2.widgets2 import DateTimeEdit as DateTimeEditBase, RatingEditor
 from calibre.library.comments import comments_to_html
 from calibre.utils.config import tweaks
 from calibre.utils.date import (
-    as_local_time, as_utc, internal_iso_format_string, is_date_undefined, now, qt_to_dt,
+    as_local_time, as_utc, internal_iso_format_string, is_date_undefined, now,
+    qt_from_dt, qt_to_dt,
 )
 from calibre.utils.icu import lower as icu_lower, sort_key
 
@@ -349,7 +350,7 @@ class DateTimeEdit(DateTimeEditBase):
         DateTimeEditBase.focusOutEvent(self, x)
 
     def set_to_today(self):
-        self.setDateTime(now())
+        self.setDateTime(qt_from_dt(now()))
 
     def set_to_clear(self):
         self.setDateTime(UNDEFINED_QDATETIME)
@@ -400,12 +401,12 @@ class DateTime(Base):
         if val is None:
             val = self.dte.minimumDateTime()
         else:
-            val = QDateTime(val)
+            val = qt_from_dt(val)
         self.dte.setDateTime(val)
 
     def getter(self):
         val = self.dte.dateTime()
-        if val <= UNDEFINED_QDATETIME:
+        if is_date_undefined(val):
             val = None
         else:
             val = qt_to_dt(val)
@@ -1251,13 +1252,13 @@ class BulkDateTime(BulkBase):
         if val is None:
             val = self.main_widget.minimumDateTime()
         else:
-            val = QDateTime(val)
+            val = qt_from_dt(val)
         self.main_widget.setDateTime(val)
         self.ignore_change_signals = False
 
     def getter(self):
         val = self.main_widget.dateTime()
-        if val <= UNDEFINED_QDATETIME:
+        if is_date_undefined(val):
             val = None
         else:
             val = qt_to_dt(val)

src/calibre/gui2/library/models.py

@@ -15,8 +15,8 @@ import traceback
 from collections import defaultdict, namedtuple
 from itertools import groupby
 from qt.core import (
-    QAbstractTableModel, QApplication, QColor, QDateTime, QFont, QFontMetrics, QIcon,
-    QImage, QModelIndex, QPainter, QPixmap, Qt, pyqtSignal,
+    QAbstractTableModel, QApplication, QColor, QFont, QFontMetrics, QIcon, QImage,
+    QModelIndex, QPainter, QPixmap, Qt, pyqtSignal,
 )
 
 from calibre import (
@@ -34,7 +34,7 @@ from calibre.library.save_to_disk import find_plugboard
 from calibre.ptempfile import PersistentTemporaryFile
 from calibre.utils.config import device_prefs, prefs, tweaks
 from calibre.utils.date import (
-    UNDEFINED_DATE, as_local_time, dt_factory, is_date_undefined, qt_to_dt,
+    UNDEFINED_DATE, dt_factory, is_date_undefined, qt_from_dt, qt_to_dt,
 )
 from calibre.utils.icu import sort_key
 from calibre.utils.localization import calibre_langcode_to_name, ngettext
@@ -919,7 +919,7 @@ class BooksModel(QAbstractTableModel):  # {{{
             elif dt == 'datetime':
                 def func(idx):
                     val = fffunc(field_obj, idfunc(idx), default_value=UNDEFINED_DATE)
-                    return None if is_date_undefined(val) else QDateTime(as_local_time(val))
+                    return None if is_date_undefined(val) else qt_from_dt(val)
             elif dt == 'rating':
                 rating_fields[field] = m['display'].get('allow_half_stars', False)
 

src/calibre/gui2/metadata/basic_widgets.py

@@ -36,7 +36,9 @@ from calibre.gui2.comments_editor import Editor
 from calibre.gui2.complete2 import EditWithComplete
 from calibre.gui2.dialogs.tag_editor import TagEditor
 from calibre.gui2.languages import LanguagesEdit as LE
-from calibre.gui2.widgets import EnLineEdit, FormatList as _FormatList, ImageView, LineEditIndicators
+from calibre.gui2.widgets import (
+    EnLineEdit, FormatList as _FormatList, ImageView, LineEditIndicators,
+)
 from calibre.gui2.widgets2 import (
     DateTimeEdit, Dialog, RatingEditor, RightClickButton, access_key,
     populate_standard_spinbox_context_menu,
@@ -46,7 +48,7 @@ from calibre.ptempfile import PersistentTemporaryFile, SpooledTemporaryFile
 from calibre.utils.config import prefs, tweaks
 from calibre.utils.date import (
     UNDEFINED_DATE, as_local_time, internal_iso_format_string, is_date_undefined,
-    local_tz, parse_only_date, qt_to_dt, utcfromtimestamp,
+    local_tz, parse_only_date, qt_from_dt, qt_to_dt, utcfromtimestamp,
 )
 from calibre.utils.filenames import make_long_path_useable
 from calibre.utils.icu import sort_key, strcmp
@@ -188,6 +190,8 @@ def make_undoable(spinbox):
             if hasattr(self, 'setDateTime'):
                 if isinstance(val, date) and not isinstance(val, datetime) and not is_date_undefined(val):
                     val = parse_only_date(val.isoformat(), assume_utc=False, as_utc=False)
+                if isinstance(val, datetime):
+                    val = qt_from_dt(val)
                 self.setDateTime(val)
             elif hasattr(self, 'setValue'):
                 self.setValue(val)

src/calibre/utils/date.py

@@ -178,6 +178,17 @@ def qt_to_dt(qdate_or_qdatetime, as_utc=True):
     return dt.astimezone(_utc_tz if as_utc else _local_tz)
 
 
+def qt_from_dt(d, as_utc=False, assume_utc=False):
+    from qt.core import QDateTime, QTimeZone
+    if d.tzinfo is None:
+        d = d.replace(tzinfo=utc_tz if assume_utc else local_tz)
+    d = d.astimezone(utc_tz)
+    ans = QDateTime.fromMSecsSinceEpoch(int(d.timestamp() * 1000), QTimeZone.utc())
+    if not as_utc:
+        ans = ans.toLocalTime()
+    return ans
+
+
 def fromtimestamp(ctime, as_utc=True):
     dt = datetime.utcfromtimestamp(ctime).replace(tzinfo=_utc_tz)
     if not as_utc: