100% Coverage for Calculation/DateTime (#1870)

* 100% Coverage for Calculation/DateTime

The code in DateTime is now completely covered.
Along the way, some errors were discovered and corrected.
- The tests which have had to be changed at the start of every year are
replaced by more robust equivalents which do not require annual changes.
- Several places in the code where Gnumeric and OpenOffice were thought to differ
from Excel do not appear to have had any justification.
I have left a comment where such code has been removed.
- Use DateTime when possible rather than date, time, or strftime functions to avoid
potential Y2038 problems.
- Some impossible code has been removed, replaced by an explanatory comment.
- NETWORKDAYS had a bug when the start date was Sunday. There had been no tests
of this condition.
- Some functions allow boolean and null arguments where a number is expected.
This is more complicated than the equivalent situations in MathTrig because
the initial date for these calculations can be Day 1 rather than Day 0.
- More testing for dates from 1900-01-01 through the fictitious
everywhere-but-Excel 1900-01-29.
    - This showed that there is an additional Excel bug - Excel evaluates
WEEKNUM(emptycell) as 0, which is not a valid result for
WEEKNUM without a second argument.
PhpSpreadsheet now duplicates this bug.
    - There is a similar and even worse bug for 1904-01-01 in 1904 calculations.
Weeknum returns 0 for this,
but returns the correct value for arguments of 0 or null.
    - DATEVALUE should accept 1900-02-29 (sigh) and relatives.
PhpSpreadsheet now duplicates this bug.
- Testing bootstrap sets default timezone. This appears to be a relic from
the releases of PHP where the unwise decision, subsequenly reversed,
was made to issue messages for
"no default timezone is set" rather than just use a sensible default.
This was a disruptive setting for some of the tests I added.
There is only one test in the entire suite which is default-timezone-dependent.
Setting and resetting of default timezone is moved to that test
(Reader/ODS/ODSTest), and out of bootstrap.
- There had been no testing of NOW() function.
- DATEVALUE test had no tests for 1904 calendar and needs some.
- DATE test changed 1900/1904 calendar in use without restoring it.
- WEEKDAY test had no tests for 1904 calendar and needs some.
    - Which revealed a bug in Shared/Date (excelToDateTimeObject was not
recognizing 1904-01-01 as valid when 1904 calendar is in use).
    - And an additional bug in that legal 1904-calendar values in the 0.0-1.0
range yielded the same "wrong" answers as 1900-calendar (see "One note" below).
Also the comment for one of the calendar-1904 tests was wrong in attempting
to identify what time of day the fraction represented.

I had wanted to break this up into a set of smaller modules, a process already
started for Engineering and MathTrig.
However the number of source code changes was sufficient that I wanted
a clean delta for this request.
If it is merged, I will work on breaking it up afterwards.

One note - Shared/Date/excelToDateTimeObject, when calendar-1900 is in use,
returns an unexpected result if its argument is between 0 and 1,
which is nominally invalid for that calendar.
It uses a base-1970 calendar in that instance. That check is not justifiable
for calendar-1904, where values in that range are legal,
so I made the check specific to calendar-1900,
and adjusted 3 1904 unit test results accordingly. However, I have to admit that
I don't understand why that check should be made even for calendar-1900.
It certainly doesn't match anything that Excel does.
I would recommend scrapping that code altogether.
If agreed, I would do this as part of the break-up into smaller modules.

Another note -
more controversially, it is clear that PhpSpreadsheet needs to support
the Excel and PHP date formats. Although it requires further study,
I am not convinced that it needs to support Unix timestamp format.
Since that is a potential source of Y2038 problems on 32-bit systems,
I would like to open a PR to deprecate the use of that format.
Please let me know if you are aware of a valid reason to continue to support it.

src/PhpSpreadsheet/Shared/Date.php

@@ -160,7 +160,7 @@ public static function excelToDateTimeObject($excelTimestamp, $timeZone = null)
     {
         $timeZone = ($timeZone === null) ? self::getDefaultTimezone() : self::validateTimeZone($timeZone);
         if (Functions::getCompatibilityMode() == Functions::COMPATIBILITY_EXCEL) {
-            if ($excelTimestamp < 1.0) {
+            if ($excelTimestamp < 1 && self::$excelCalendar === self::CALENDAR_WINDOWS_1900) {
                 // Unix timestamp base date
                 $baseDate = new \DateTime('1970-01-01', $timeZone);
             } else {

tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php

@@ -9,11 +9,21 @@
 
 class DateTest extends TestCase
 {
+    private $returnDateType;
+
+    private $excelCalendar;
+
     protected function setUp(): void
     {
-        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
+        $this->returnDateType = Functions::getReturnDateType();
+        $this->excelCalendar = Date::getExcelCalendar();
         Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
-        Date::setExcelCalendar(Date::CALENDAR_WINDOWS_1900);
+    }
+
+    protected function tearDown(): void
+    {
+        Functions::setReturnDateType($this->returnDateType);
+        Date::setExcelCalendar($this->excelCalendar);
     }
 
     /**

tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php

@@ -2,6 +2,7 @@
 
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
+use DateTimeImmutable;
 use DateTimeInterface;
 use PhpOffice\PhpSpreadsheet\Calculation\DateTime;
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
@@ -10,11 +11,21 @@
 
 class DateValueTest extends TestCase
 {
+    private $returnDateType;
+
+    private $excelCalendar;
+
     protected function setUp(): void
     {
-        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
+        $this->returnDateType = Functions::getReturnDateType();
+        $this->excelCalendar = Date::getExcelCalendar();
         Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
-        Date::setExcelCalendar(Date::CALENDAR_WINDOWS_1900);
+    }
+
+    protected function tearDown(): void
+    {
+        Functions::setReturnDateType($this->returnDateType);
+        Date::setExcelCalendar($this->excelCalendar);
     }
 
     /**
@@ -25,7 +36,21 @@ protected function setUp(): void
      */
     public function testDATEVALUE($expectedResult, $dateValue): void
     {
-        $result = DateTime::DATEVALUE($dateValue);
+        // Loop to avoid extraordinarily rare edge case where first calculation
+        // and second do not take place on same day.
+        do {
+            $dtStart = new DateTimeImmutable();
+            $startDay = $dtStart->format('d');
+            if (is_string($expectedResult)) {
+                $replYMD = str_replace('Y', date('Y'), $expectedResult);
+                if ($replYMD !== $expectedResult) {
+                    $expectedResult = DateTime::DATEVALUE($replYMD);
+                }
+            }
+            $result = DateTime::DATEVALUE($dateValue);
+            $dtEnd = new DateTimeImmutable();
+            $endDay = $dtEnd->format('d');
+        } while ($startDay !== $endDay);
         self::assertEqualsWithDelta($expectedResult, $result, 1E-8);
     }
 
@@ -55,4 +80,13 @@ public function testDATEVALUEtoDateTimeObject(): void
         //    ... with the correct value
         self::assertEquals($result->format('d-M-Y'), '31-Jan-2012');
     }
+
+    public function testDATEVALUEwith1904Calendar(): void
+    {
+        Date::setExcelCalendar(Date::CALENDAR_MAC_1904);
+        self::assertEquals(5428, DateTime::DATEVALUE('1918-11-11'));
+        self::assertEquals(0, DateTime::DATEVALUE('1904-01-01'));
+        self::assertEquals('#VALUE!', DateTime::DATEVALUE('1903-12-31'));
+        self::assertEquals('#VALUE!', DateTime::DATEVALUE('1900-02-29'));
+    }
 }

tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NowTest.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
+
+use DateTimeImmutable;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PHPUnit\Framework\TestCase;
+
+class NowTest extends TestCase
+{
+    public function testNow(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        // Loop to avoid rare edge case where first calculation
+        // and second do not take place in same second.
+        do {
+            $dtStart = new DateTimeImmutable();
+            $startSecond = $dtStart->format('s');
+            $sheet->setCellValue('A1', '=NOW()');
+            $dtEnd = new DateTimeImmutable();
+            $endSecond = $dtEnd->format('s');
+        } while ($startSecond !== $endSecond);
+        //echo("\n"); var_dump($sheet->getCell('A1')->getCalculatedValue()); echo ("\n");
+        $sheet->setCellValue('B1', '=YEAR(A1)');
+        $sheet->setCellValue('C1', '=MONTH(A1)');
+        $sheet->setCellValue('D1', '=DAY(A1)');
+        $sheet->setCellValue('E1', '=HOUR(A1)');
+        $sheet->setCellValue('F1', '=MINUTE(A1)');
+        $sheet->setCellValue('G1', '=SECOND(A1)');
+        self::assertEquals($dtStart->format('Y'), $sheet->getCell('B1')->getCalculatedValue());
+        self::assertEquals($dtStart->format('m'), $sheet->getCell('C1')->getCalculatedValue());
+        self::assertEquals($dtStart->format('d'), $sheet->getCell('D1')->getCalculatedValue());
+        self::assertEquals($dtStart->format('H'), $sheet->getCell('E1')->getCalculatedValue());
+        self::assertEquals($dtStart->format('i'), $sheet->getCell('F1')->getCalculatedValue());
+        self::assertEquals($dtStart->format('s'), $sheet->getCell('G1')->getCalculatedValue());
+    }
+}

tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php

@@ -9,11 +9,20 @@
 
 class TimeTest extends TestCase
 {
+    private $returnDateType;
+
+    private $calendar;
+
     protected function setUp(): void
     {
-        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
-        Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
-        Date::setExcelCalendar(Date::CALENDAR_WINDOWS_1900);
+        $this->returnDateType = Functions::getReturnDateType();
+        $this->calendar = Date::getExcelCalendar();
+    }
+
+    protected function tearDown(): void
+    {
+        Functions::setReturnDateType($this->returnDateType);
+        Date::setExcelCalendar($this->calendar);
     }
 
     /**
@@ -23,6 +32,7 @@ protected function setUp(): void
      */
     public function testTIME($expectedResult, ...$args): void
     {
+        Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
         $result = DateTime::TIME(...$args);
         self::assertEqualsWithDelta($expectedResult, $result, 1E-8);
     }
@@ -52,4 +62,20 @@ public function testTIMEtoDateTimeObject(): void
         //    ... with the correct value
         self::assertEquals($result->format('H:i:s'), '07:30:20');
     }
+
+    public function testTIME1904(): void
+    {
+        Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
+        Date::setExcelCalendar(Date::CALENDAR_MAC_1904);
+        $result = DateTime::TIME(0, 0, 0);
+        self::assertEquals(0, $result);
+    }
+
+    public function testTIME1900(): void
+    {
+        Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
+        Date::setExcelCalendar(Date::CALENDAR_WINDOWS_1900);
+        $result = DateTime::TIME(0, 0, 0);
+        self::assertEquals(0, $result);
+    }
 }

tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekDayTest.php

@@ -3,17 +3,21 @@
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\DateTime;
-use PhpOffice\PhpSpreadsheet\Calculation\Functions;
 use PhpOffice\PhpSpreadsheet\Shared\Date;
 use PHPUnit\Framework\TestCase;
 
 class WeekDayTest extends TestCase
 {
+    private $excelCalendar;
+
     protected function setUp(): void
     {
-        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
-        Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
-        Date::setExcelCalendar(Date::CALENDAR_WINDOWS_1900);
+        $this->excelCalendar = Date::getExcelCalendar();
+    }
+
+    protected function tearDown(): void
+    {
+        Date::setExcelCalendar($this->excelCalendar);
     }
 
     /**
@@ -31,4 +35,12 @@ public function providerWEEKDAY()
     {
         return require 'tests/data/Calculation/DateTime/WEEKDAY.php';
     }
+
+    public function testWEEKDAYwith1904Calendar(): void
+    {
+        Date::setExcelCalendar(Date::CALENDAR_MAC_1904);
+        self::assertEquals(7, DateTime::WEEKDAY('1904-01-02'));
+        self::assertEquals(6, DateTime::WEEKDAY('1904-01-01'));
+        self::assertEquals(6, DateTime::WEEKDAY(null));
+    }
 }

tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekNumTest.php

@@ -3,17 +3,21 @@
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\DateTime;
-use PhpOffice\PhpSpreadsheet\Calculation\Functions;
 use PhpOffice\PhpSpreadsheet\Shared\Date;
 use PHPUnit\Framework\TestCase;
 
 class WeekNumTest extends TestCase
 {
+    private $excelCalendar;
+
     protected function setUp(): void
     {
-        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
-        Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
-        Date::setExcelCalendar(Date::CALENDAR_WINDOWS_1900);
+        $this->excelCalendar = Date::getExcelCalendar();
+    }
+
+    protected function tearDown(): void
+    {
+        Date::setExcelCalendar($this->excelCalendar);
     }
 
     /**
@@ -31,4 +35,14 @@ public function providerWEEKNUM()
     {
         return require 'tests/data/Calculation/DateTime/WEEKNUM.php';
     }
+
+    public function testWEEKNUMwith1904Calendar(): void
+    {
+        Date::setExcelCalendar(Date::CALENDAR_MAC_1904);
+        self::assertEquals(27, DateTime::WEEKNUM('2004-07-02'));
+        self::assertEquals(1, DateTime::WEEKNUM('1904-01-02'));
+        self::assertEquals(1, DateTime::WEEKNUM(null));
+        // The following is a bug in Excel.
+        self::assertEquals(0, DateTime::WEEKNUM('1904-01-01'));
+    }
 }

tests/PhpSpreadsheetTests/Reader/Ods/OdsTest.php

@@ -15,6 +15,19 @@
  */
 class OdsTest extends TestCase
 {
+    private $timeZone;
+
+    protected function setUp(): void
+    {
+        $this->timeZone = date_default_timezone_get();
+        date_default_timezone_set('UTC');
+    }
+
+    protected function tearDown(): void
+    {
+        date_default_timezone_set($this->timeZone);
+    }
+
     /**
      * @var Spreadsheet
      */
@@ -153,13 +166,13 @@ public function testReadValueAndComments(): void
         self::assertEquals(0, $firstSheet->getCell('G10')->getValue());
 
         self::assertEquals(DataType::TYPE_NUMERIC, $firstSheet->getCell('A10')->getDataType()); // Date
-        self::assertEquals(22269.0, $firstSheet->getCell('A10')->getValue());
+        self::assertEquals('19-Dec-60', $firstSheet->getCell('A10')->getFormattedValue());
 
         self::assertEquals(DataType::TYPE_NUMERIC, $firstSheet->getCell('A13')->getDataType()); // Time
-        self::assertEquals(25569.0625, $firstSheet->getCell('A13')->getValue());
+        self::assertEquals('2:30:00', $firstSheet->getCell('A13')->getFormattedValue());
 
         self::assertEquals(DataType::TYPE_NUMERIC, $firstSheet->getCell('A15')->getDataType()); // Date + Time
-        self::assertEquals(22269.0625, $firstSheet->getCell('A15')->getValue());
+        self::assertEquals('19-Dec-60 1:30:00', $firstSheet->getCell('A15')->getFormattedValue());
 
         self::assertEquals(DataType::TYPE_NUMERIC, $firstSheet->getCell('A11')->getDataType()); // Fraction
 

tests/bootstrap.php

@@ -3,4 +3,4 @@
 setlocale(LC_ALL, 'en_US.utf8');
 
 // PHP 5.3 Compat
-date_default_timezone_set('Europe/London');
+//date_default_timezone_set('Europe/London');