This closes qax-os#409 Remove UTC timezone requirement from date.go (q…

…ax-os#853)

According to issue qax-os#409

There is absolutely no reason for the timezone to be in UTC, and converting the local times to UTC while keeping values is hacky at least.

Excel has no understanding of timezones, hence the user of this library should know what timezone their values are supposed to be, by following the timezone within their timeTime structs.

date.go

@@ -30,13 +30,6 @@ var (
 func timeToExcelTime(t time.Time) (float64, error) {
 	// TODO in future this should probably also handle date1904 and like TimeFromExcelTime
 
-	// Force user to explicit convet passed value to UTC time.
-	// Because for example 1900-01-01 00:00:00 +0300 MSK converts to 1900-01-01 00:00:00 +0230 LMT
-	// probably due to daylight saving.
-	if t.Location() != time.UTC {
-		return 0.0, ErrToExcelTime
-	}
-
 	if t.Before(excelMinTime1900) {
 		return 0.0, nil
 	}

date_test.go

@@ -55,7 +55,7 @@ func TestTimeToExcelTime_Timezone(t *testing.T) {
 	for i, test := range trueExpectedDateList {
 		t.Run(fmt.Sprintf("TestData%d", i+1), func(t *testing.T) {
 			_, err := timeToExcelTime(test.GoValue.In(location))
-			assert.EqualError(t, err, ErrToExcelTime.Error())
+			assert.NoError(t, err)
 		})
 	}
 }

excelize_test.go

@@ -144,7 +144,7 @@ func TestOpenFile(t *testing.T) {
 
 	assert.NoError(t, f.SetCellValue("Sheet2", "G2", nil))
 
-	assert.EqualError(t, f.SetCellValue("Sheet2", "G4", time.Now()), ErrToExcelTime.Error())
+	assert.NoError(t, f.SetCellValue("Sheet2", "G4", time.Now()))
 
 	assert.NoError(t, f.SetCellValue("Sheet2", "G4", time.Now().UTC()))
 	// 02:46:40

stream_test.go

@@ -57,7 +57,7 @@ func TestStreamWriter(t *testing.T) {
 	assert.NoError(t, err)
 	assert.NoError(t, streamWriter.SetRow("A4", []interface{}{Cell{StyleID: styleID}, Cell{Formula: "SUM(A10,B10)"}}))
 	assert.NoError(t, streamWriter.SetRow("A5", []interface{}{&Cell{StyleID: styleID, Value: "cell"}, &Cell{Formula: "SUM(A10,B10)"}}))
-	assert.EqualError(t, streamWriter.SetRow("A6", []interface{}{time.Now()}), ErrToExcelTime.Error())
+	assert.NoError(t, streamWriter.SetRow("A6", []interface{}{time.Now()}))
 
 	for rowID := 10; rowID <= 51200; rowID++ {
 		row := make([]interface{}, 50)