diff --git a/client/helper.cpp b/client/helper.cpp
index 9ef1419..eb3b70d 100644
--- a/client/helper.cpp
+++ b/client/helper.cpp
@@ -44,6 +44,35 @@ void theme::applyCurrent(Settings& settings)
         qApp->setStyleSheet("");
 }
 
+date::date()
+{}
+
+date::date(int y, int m, int d)
+    :mYear(y), mMonth(m), mDay(d)
+{
+}
+
+time_t date::toTimestamp() const
+{
+    struct tm t;
+    memset(&t, 0, sizeof t);
+    t.tm_year = mYear - 1900;
+    t.tm_mon = mMonth - 1;
+    t.tm_mday = mDay;
+    return mktime(&t);
+}
+
+date date::fromTimestamp(time_t timestamp)
+{
+    struct tm t;
+    memset(&t, 0, sizeof t);
+    t = *localtime(&timestamp);
+    date r;
+    r.mDay = t.tm_mday;
+    r.mMonth = t.tm_mon + 1;
+    r.mYear = t.tm_year + 1900;
+    return r;
+}
 
 std::string chrono::secondsToDisplay(int seconds, bool showSeconds)
 {
@@ -66,6 +95,13 @@ std::string chrono::timeToStr(time_t timestamp)
     return buf;
 }
 
+std::string chrono::timeToLocalStr(time_t timestamp)
+{
+    char buf[128];
+    strftime(buf, sizeof buf, "%FT%TZ", localtime(&timestamp));
+    return buf;
+}
+
 time_t chrono::strToTime(const std::string& s)
 {
     struct tm t;
diff --git a/client/helper.h b/client/helper.h
index 10514a0..1b53782 100644
--- a/client/helper.h
+++ b/client/helper.h
@@ -13,12 +13,17 @@ namespace helper
         static void applyCurrent(Settings& settings);
     };
 
+    // date is always local. year, month & day number is natural (NO start from zero, NO delta with 1900 year etc.)
     struct date
     {
         int mYear = -1, mMonth = -1, mDay = -1;
 
-        time_t toTimestamp();
-        static date fromTimestamp();
+        date();
+        date(int y, int m, int d);
+
+        // Timestamp is always UTC! But date is always local!
+        time_t toTimestamp() const;
+        static date fromTimestamp(time_t timestamp);
     };
 
     class chrono
@@ -26,7 +31,9 @@ namespace helper
     public:
         static std::string secondsToDisplay(int seconds, bool showSeconds);
         static std::string timeToStr(time_t timestamp);
+        static std::string timeToLocalStr(time_t timestamp);
         static time_t strToTime(const std::string& s);
+        static struct tm localtime(time_t timestamp);
     };
 
 
diff --git a/client/main.cpp b/client/main.cpp
index bf6e729..5310ac2 100644
--- a/client/main.cpp
+++ b/client/main.cpp
@@ -7,7 +7,7 @@
 int main(int argc, char *argv[])
 {
     QApplication a(argc, argv);
-    ThemeHelper::applyCurrentTheme(Settings::instance());
+    helper::theme::applyCurrent(Settings::instance());
 
     MainWindow w;
     w.layout()->invalidate();
diff --git a/client/mainwindow.cpp b/client/mainwindow.cpp
index cf76ddd..77a207c 100644
--- a/client/mainwindow.cpp
+++ b/client/mainwindow.cpp
@@ -36,7 +36,7 @@ MainWindow::MainWindow(QWidget *parent) :
 {
     mSettings = QSharedPointer<Settings>(new Settings());
 
-    ThemeHelper::applyCurrentTheme(*mSettings);
+    helper::theme::applyCurrent(*mSettings);
 
     mAttachmentsAction = nullptr;
     mAttachmentsLabel = nullptr;
@@ -51,7 +51,7 @@ MainWindow::MainWindow(QWidget *parent) :
 
     // Hide Find line edit for now
     ui->mFindFrame->setVisible(false);
-    EscapeKeyEventFilter* eventFilter = new EscapeKeyEventFilter(ui->mFindEdit);
+    helper::EscapeKeyEventFilter* eventFilter = new helper::EscapeKeyEventFilter(ui->mFindEdit);
     connect(eventFilter, SIGNAL(escapePressed(QObject*)), this, SLOT(findRejected(QObject*)));
     ui->mFindEdit->installEventFilter(eventFilter);
 
@@ -854,7 +854,7 @@ void MainWindow::startTracking()
     // Trigger permission dialog if needed
     if (mSettings->data()[KEY_SMART_STOP].toBool())
     {
-        if (!ActivityTrackerHelper::ensureSmartTrackingIsPossible())
+        if (!helper::activityTracker::ensureSmartTrackingIsPossible())
             mTrayIcon->showMessage(tr("No smart tracking stop/start"), tr("Problem with obtaining permissions"), QSystemTrayIcon::Warning);
     }
 
@@ -992,7 +992,7 @@ void MainWindow::updateData()
 
         if (saveToDb)
             mLogger->log("Flushing timeline to DB start");
-        mCurrentTask->timeline()->flush(saveToDb, QDateTime::currentDateTimeUtc());
+        mCurrentTask->timeline()->flush(saveToDb, QDateTime::currentDateTimeUtc().toTime_t());
         if (saveToDb)
         {
             mLastTimelineFlush = QDateTime::currentDateTimeUtc();
@@ -1236,8 +1236,8 @@ void MainWindow::showTimeForSelectedTask()
 
         int spentSecondsToday = t->timeline()->today();
         int spentSecondsMonth = t->timeline()->month();
-        ui->mTodaySpentTimeLabel->setText(TimeHelper::secondsToDisplay(spentSecondsToday, showSeconds));
-        ui->mThisMonthSpentTimeLabel->setText(TimeHelper::secondsToDisplay(spentSecondsMonth, showSeconds));
+        ui->mTodaySpentTimeLabel->setText(QString::fromStdString(helper::chrono::secondsToDisplay(spentSecondsToday, showSeconds)));
+        ui->mThisMonthSpentTimeLabel->setText(QString::fromStdString(helper::chrono::secondsToDisplay(spentSecondsMonth, showSeconds)));
     }
 }
 
@@ -1256,7 +1256,7 @@ void MainWindow::showTimeForTrackingTask()
             t = t->parent();
         }
         int spentSecondsToday = mCurrentTask->timeline()->today();
-        QString timeString = TimeHelper::secondsToDisplay(spentSecondsToday, showSeconds);
+        QString timeString = QString::fromStdString(helper::chrono::secondsToDisplay(spentSecondsToday, showSeconds));
         path += " : " + timeString;
         mCurrentIntervalLabel->setText(path);
 
@@ -1301,7 +1301,7 @@ void MainWindow::updateTrayIcon(TrayShowMessage flag)
     {
         bool showSeconds = mSettings->data()[KEY_SHOW_SECONDS].toBool();
         int spentSecondsToday = mCurrentTask->timeline()->today();
-        QString timeString = TimeHelper::secondsToDisplay(spentSecondsToday, showSeconds);
+        QString timeString = helper::chrono::secondsToDisplay(spentSecondsToday, showSeconds);
         tooltip = tr("Litt is tracking ") + mCurrentTask->title() + ".\n" +
                 tr("Time spent today for this task is ") + timeString;
     }
diff --git a/client/preferencesdlg.cpp b/client/preferencesdlg.cpp
index 35d6418..23838b7 100644
--- a/client/preferencesdlg.cpp
+++ b/client/preferencesdlg.cpp
@@ -35,7 +35,7 @@ PreferencesDlg::PreferencesDlg(QWidget *parent, Settings& settings) :
     if (settings.data().value(KEY_DB_FILENAME_SPECIFIED).toBool())
         ui->mDatabaseLocation->setText(settings.data().value(KEY_DB_FILENAME).toString());
     else
-        ui->mDatabaseLocation->setText(PathHelper::pathToDatabase());
+        ui->mDatabaseLocation->setText(helper::path::pathToDatabase());
 
     // Use stop on idle ?
     ui->mSmartStopTracking->setChecked(GET_BOOL(KEY_SMART_STOP));
@@ -61,7 +61,7 @@ PreferencesDlg::~PreferencesDlg()
 
 void PreferencesDlg::selectDatabase()
 {
-    QFileDialog dlg(this, tr("Select database to use"), PathHelper::pathToDesktop());
+    QFileDialog dlg(this, tr("Select database to use"), helper::path::pathToDesktop());
     dlg.setAcceptMode(QFileDialog::AcceptSave);
     dlg.setFileMode(QFileDialog::AnyFile);
     if (dlg.exec() == QDialog::Accepted)
@@ -95,7 +95,7 @@ void PreferencesDlg::smartStopSettingChanged(bool v)
 {
     if (v)
     {
-        if (!ActivityTrackerHelper::ensureSmartTrackingIsPossible())
+        if (!helper::activityTracker::ensureSmartTrackingIsPossible())
             ui->mSmartStopTracking->setChecked(false);
     }
     allowStartAfterIdleControls();
@@ -127,5 +127,5 @@ void PreferencesDlg::allowStartAfterIdleControls()
 
 void PreferencesDlg::applyTheme()
 {
-    ThemeHelper::applyCurrentTheme(mSettings);
+    helper::theme::applyCurrent(mSettings);
 }
diff --git a/client/settings.cpp b/client/settings.cpp
index 43a6e2e..c2cc9e4 100644
--- a/client/settings.cpp
+++ b/client/settings.cpp
@@ -20,7 +20,7 @@ QVariantMap& Settings::data()
 
 void Settings::save()
 {
-    QSettings settings(PathHelper::pathToSettings(), QSettings::IniFormat);
+    QSettings settings(helper::path::pathToSettings(), QSettings::IniFormat);
     settings.clear();
     for (const QString& e: data().keys())
     {
@@ -30,7 +30,7 @@ void Settings::save()
 
 void Settings::load()
 {
-    QSettings settings(PathHelper::pathToSettings(), QSettings::IniFormat);
+    QSettings settings(helper::path::pathToSettings(), QSettings::IniFormat);
     mData.clear();
     const QStringList keys = settings.allKeys();
     for (const QString& k: keys)
diff --git a/client/task.cpp b/client/task.cpp
index 5e5e7ae..c334b87 100644
--- a/client/task.cpp
+++ b/client/task.cpp
@@ -101,7 +101,7 @@ void TimeRecord::setStartTime(const time_t &startTime)
 
 int TimeRecord::length()
 {
-    return (int)(mEndTime - mStartTime);
+    return static_cast<int>(mEndTime - mStartTime);
 }
 
 Id TimeRecord::id() const
@@ -140,10 +140,9 @@ void TimeRecord::save()
     {
         SQLite::Statement q(Storage::instance().database(), "insert into timeline(id, starttime, endtime, taskid, removed) values (NULL, :starttime, :endtime, :taskid, :removed)");
 
-
-        q.bind(":starttime", TimeHelper::timeToStr(mStartTime));
-        q.bind(":endtime", TimeHelper::timeToStr(mEndTime));
-        q.bind(":taskid", (sqlite3_int64)mTaskId);
+        q.bind(":starttime", helper::chrono::timeToStr(mStartTime));
+        q.bind(":endtime", helper::chrono::timeToStr(mEndTime));
+        q.bind(":taskid", static_cast<sqlite3_int64>(mTaskId));
         q.bind(":removed", 0);
         if (q.exec())
             mId = Storage::instance().database().getLastInsertRowid();
@@ -152,10 +151,10 @@ void TimeRecord::save()
     {
         SQLite::Statement q(Storage::instance().database(),
                             "update timeline set starttime = :starttime, endtime = :endtime, taskid = :taskid, removed = 0 where id = :id");
-        q.bind(":starttime", TimeHelper::timeToStr(mStartTime));
-        q.bind(":endtime", TimeHelper::timeToStr(mEndTime));
-        q.bind(":taskid", (sqlite3_int64)mTaskId);
-        q.bind(":id", (sqlite3_int64)mId);
+        q.bind(":starttime", helper::chrono::timeToStr(mStartTime));
+        q.bind(":endtime", helper::chrono::timeToStr(mEndTime));
+        q.bind(":taskid", static_cast<sqlite3_int64>(mTaskId));
+        q.bind(":id", static_cast<sqlite3_int64>(mId));
         q.exec();
     }
 }
@@ -163,7 +162,7 @@ void TimeRecord::save()
 void TimeRecord::deleteRecord()
 {
     SQLite::Statement q(Storage::instance().database(), "update timeline set removed = 1 where id = :id");
-    q.bind(":id", (sqlite3_int64)mId);
+    q.bind(":id", static_cast<sqlite3_int64>(mId));
     q.exec();
 }
 
@@ -178,9 +177,9 @@ TimeLine::~TimeLine()
 int TimeLine::findTotalTime()
 {
     int result = 0;
-    for(auto& t: mData.begin())
+    for(auto& t: mData)
     {
-        int delta = t.endTime() - t.startTime();
+        int delta = static_cast<int>(t.endTime() - t.startTime());
         result += delta + 1;
     }
     return result;
@@ -253,7 +252,7 @@ TimeRecord* TimeLine::hasTimePoint(time_t t)
                               });
 
     if (result == mData.end())
-        tr = &mData.last();
+        tr = &mData.back();
     else
         if (result != mData.begin())
             tr = &(*(--result));
@@ -281,7 +280,7 @@ bool TimeLine::hasIntersection(const TimeRecord &interval)
     if (result == mData.end())
     {
         // There is time record which start point is lesser than interval.startTime()
-        return (mData.last().endTime() >= interval.startTime());
+        return (mData.back().endTime() >= interval.startTime());
     }
     else
         if (result != mData.begin())
@@ -304,7 +303,7 @@ bool TimeLine::hasIntersection(const TimeRecord &interval)
 void TimeLine::insertInterval(const TimeRecord &interval)
 {
     mData.push_back(interval);
-    mData.last().save();
+    mData.back().save();
 
     sortData();
 }
@@ -323,7 +322,7 @@ bool TimeLine::removeInterval(const TimeRecord &interval)
     if (result == mData.end())
     {
         // There is time record which start point is lesser than interval.startTime()
-        if (mData.last().id() == interval.id())
+        if (mData.back().id() == interval.id())
         {
             // Remove from DB
             mData.back().deleteRecord();
@@ -489,8 +488,8 @@ void TimeLine::load()
     q.bind(":taskid", (sqlite3_int64)mTaskId);
     while (q.executeStep())
     {
-        time_t start = TimeHelper::strToTime(q.getColumn(1).getText());
-        time_t stop = TimeHelper::strToTime(q.getColumn(2).getText());
+        time_t start = helper::chrono::strToTime(q.getColumn(1).getText());
+        time_t stop = helper::chrono::strToTime(q.getColumn(2).getText());
 
         TimeRecord tr;
         tr.setId(q.getColumn(0).getInt64());
@@ -532,9 +531,8 @@ void TimeLine::getYears(std::set<int>& years)
     if (mData.empty())
         return;
 
-    struct tm t1, t2;
-    localtime(&mData.front().startTime(), &t1);
-    localtime(&mData.back().startTime(), &t2);
+    time_t starttime_1 = mData.front().startTime(), starttime_2 = mData.back().startTime();
+    struct tm t1 = *localtime(&starttime_1), t2 = *localtime(&starttime_2);
 
     // Find lower bound of years - it is first time record
     int year1 = t1.tm_year + 1900;
@@ -556,7 +554,7 @@ void TimeLine::getYears(std::set<int>& years)
         if (iter != mData.end())
         {
             // Get current year
-            struct tm ct; localtime(&iter->startTime(), &ct);
+            struct tm ct = helper::chrono::localtime(iter->startTime());
             if (ct.tm_year + 1900 <= year)
                 years.insert(year);
         }
@@ -571,15 +569,17 @@ void TimeLine::getMonthes(int year, std::set<int>& result)
         QDate monthEnd(year, month, monthBegin.daysInMonth());
 
         // Find range for every month in year [lowest, higher)
-        TimeArray::iterator lowest = std::lower_bound(mData.begin(), mData.end(), monthBegin, [] (const TimeRecord& tr, const QDate& d) { return tr.endTime().toLocalTime().date() < d;});
+        TimeArray::iterator lowest = std::lower_bound(mData.begin(), mData.end(), monthBegin,
+                                                      [] (const TimeRecord& tr, const QDate& d)
+                                                      { return tr.endTime() < QDateTime(d).toTime_t();});
         //TimeArray::iterator higher = std::upper_bound(mData.begin(), mData.end(), monthEnd, [] (const TimeRecord& tr, const QDate& d) { return tr.startTime().toLocalTime().date() < d;});
         if (lowest != mData.end())
         {
-            int currentYear = lowest->startTime().toLocalTime().date().year();
-            int currentMonth = lowest->startTime().toLocalTime().date().month();
-            if (currentYear > year)
+            // Current date is local time!
+            helper::date currentDate = helper::date::fromTimestamp(lowest->startTime());
+            if (currentDate.mYear > year)
                 continue;
-            if (currentYear == year && currentMonth > month)
+            if (currentDate.mYear == year && currentDate.mMonth > month)
                 continue;
 
             result.insert(month);
@@ -594,17 +594,19 @@ void TimeLine::getDays(int year, int month, std::set<int>& result)
     {
         QDate currentDay(year, month, day);
 
-        TimeArray::iterator lowest = std::lower_bound(mData.begin(), mData.end(), currentDay, [] (const TimeRecord& tr, const QDate& d) { return tr.endTime().toLocalTime().date() < d;});
+        TimeArray::iterator lowest = std::lower_bound(mData.begin(), mData.end(), currentDay,
+                                                      [] (const TimeRecord& tr, const QDate& d)
+                                                      {
+                                                          return tr.endTime() < QDateTime(d).toTime_t();
+                                                      });
         if (lowest != mData.end())
         {
-            int startYear = lowest->startTime().toLocalTime().date().year();
-            int startMonth = lowest->startTime().toLocalTime().date().month();
-            int startDay = lowest->startTime().toLocalTime().date().day();
-            if (startYear > year)
+            helper::date startDate = helper::date::fromTimestamp(lowest->startTime());
+            if (startDate.mYear > year)
                 continue;
-            if (startYear == year && startMonth > month)
+            if (startDate.mYear == year && startDate.mMonth > month)
                 continue;
-            if (startYear == year && startMonth == month && startDay > day)
+            if (startDate.mYear == year && startDate.mMonth == month && startDate.mDay > day)
                 continue;
 
             result.insert(day);
@@ -618,30 +620,36 @@ int TimeLine::getTime(int year, int month, int day, std::vector<TimeRecord>* int
     QDate d(year, month, day);
 
     // Find range of related records [lowest, higher)
-    TimeArray::iterator lowest = std::lower_bound(mData.begin(), mData.end(), d, [] (const TimeRecord& tr, const QDate& d) { return tr.endTime().toLocalTime().date() < d;});
+    TimeArray::iterator lowest = std::lower_bound(mData.begin(), mData.end(), d, [] (const TimeRecord& tr, const QDate& d)
+                                                                                 {
+                                                                                    return tr.endTime() < QDateTime(d).toTime_t();
+                                                                                 });
     //TimeArray::iterator higher = std::upper_bound(mData.begin(), mData.end(), d, [] (const QDate& d, const TimeRecord& tr) { return tr.startTime().toLocalTime().date() < d;});
 
     for (;lowest != mData.end();/*&& lowest != higher;*/ lowest++)
     {
         TimeRecord& tr = *lowest;
-        if (tr.startTime().toLocalTime().date().year() > year)
+
+        helper::date startDate = helper::date::fromTimestamp(tr.startTime());
+
+        if (startDate.mYear > year)
             break;
-        if (tr.startTime().toLocalTime().date().year() == year && tr.startTime().toLocalTime().date().month() > month)
+        if (startDate.mYear == year && startDate.mMonth > month)
             break;
 
-        if (tr.startTime().toLocalTime().date().year() == year &&
-                tr.startTime().toLocalTime().date().month() == month &&
-                tr.startTime().toLocalTime().date().day() > day)
+        if (startDate.mYear == year &&
+            startDate.mMonth == month &&
+            startDate.mDay > day)
             break;
 
-        QDateTime dayBegin(d, QTime(0, 0, 0));
-        QDateTime dayEnd(d, QTime(23, 59, 59));
+        time_t dayBegin = helper::date{year, month, day}.toTimestamp();
+        time_t dayEnd = dayBegin + 86399;
 
-        if (tr.startTime().toLocalTime().secsTo(dayBegin) < 0)
-            dayBegin = tr.startTime().toLocalTime(); // Time record begin is later than begin of the day
+        if (tr.startTime() > dayBegin)
+            dayBegin = tr.startTime(); // Time record begin is later than begin of the day
 
-        if (tr.endTime().toLocalTime().secsTo(dayEnd) > 0)
-            dayEnd = tr.endTime().toLocalTime();
+        if (tr.endTime() < dayEnd)
+            dayEnd = tr.endTime();
 
         if (intervals)
         {
diff --git a/client/task.h b/client/task.h
index 91369be..22c591d 100644
--- a/client/task.h
+++ b/client/task.h
@@ -63,7 +63,7 @@ protected:
     bool mSaved;
 };
 
-typedef QVector<TimeRecord> TimeArray;
+typedef std::vector<TimeRecord> TimeArray;
 
 typedef std::set<int> HoursSet;
 typedef std::map<int, QSharedPointer<HoursSet> > DaysMap;
diff --git a/client/timereportwizard.cpp b/client/timereportwizard.cpp
index dcfc3c9..e5772e1 100644
--- a/client/timereportwizard.cpp
+++ b/client/timereportwizard.cpp
@@ -140,14 +140,14 @@ void ReportViewPage::generateReport()
   {
     int individualTime = t->getReportedTime();
     bool showSeconds = mSettings.data()[KEY_SHOW_SECONDS].toBool();
-    QString l1 = TimeHelper::secondsToDisplay(individualTime, showSeconds);
+    QString l1 = helper::chrono::secondsToDisplay(individualTime, showSeconds);
     report += t->path() + " : " + l1;
     //if (mSettings.data()[KEY_CUMULATIVE_REPORT].toBool())
     {
       int childrenTime = t->getChildrenReportedTime();
       if (childrenTime)
       {
-        QString l2 = TimeHelper::secondsToDisplay(individualTime + childrenTime, showSeconds);
+        QString l2 = helper::chrono::secondsToDisplay(individualTime + childrenTime, showSeconds);
         report += ". Including subtasks time: " + l2;
       }
     }
diff --git a/client/timetreemodel.cpp b/client/timetreemodel.cpp
index 0ed661c..9c0e7bc 100644
--- a/client/timetreemodel.cpp
+++ b/client/timetreemodel.cpp
@@ -305,7 +305,7 @@ QVariant TimeTreeModel::data(const QModelIndex &index, int role) const
         tr = intervals[index.row()];
 
         // Intervals are in local time already
-        return QString("%1 - %2").arg(tr.startTime().time().toString(mTimeFormat), tr.endTime().time().toString(mTimeFormat));
+        return QString("%1 - %2").arg(helper::chronotr.startTime().time().toString(mTimeFormat), tr.endTime().time().toString(mTimeFormat));
 
     default:
         return QVariant();