datetime: fix interval arithmetic with timezones

Tarantool used to ignore timezone difference (offset) for a datetime
interval calculations due to a bug [1]. We have to fix it too since
we relied on the wrong behavior.

1. tarantool/tarantool#7698

Author: oleg-jukovec

CHANGELOG.md

@@ -35,6 +35,7 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
 - Decimal package use a test function GetNumberLength instead of a
   package-level function getNumberLength (#219)
 - Datetime location after encode + decode is unequal (#217)
+- Wrong interval arithmetic with timezones (#221)
 
 ## [1.8.0] - 2022-08-17
 

datetime/datetime.go

@@ -220,6 +220,9 @@ func (dtime *Datetime) Sub(ival Interval) (*Datetime, error) {
 func (dtime *Datetime) Interval(next *Datetime) Interval {
 	curIval := intervalFromDatetime(dtime)
 	nextIval := intervalFromDatetime(next)
+	_, curOffset := dtime.time.Zone()
+	_, nextOffset := next.time.Zone()
+	curIval.Min -= int64(curOffset-nextOffset) / 60
 	return nextIval.Sub(curIval)
 }
 

datetime/datetime_test.go

@@ -321,7 +321,7 @@ func TestDatetimeAddOutOfRange(t *testing.T) {
 }
 
 func TestDatetimeInterval(t *testing.T) {
-	var first = "2015-03-20T17:50:56.000000009Z"
+	var first = "2015-03-20T17:50:56.000000009+01:00"
 	var second = "2013-01-31T17:51:56.000000009Z"
 
 	tmFirst, err := time.Parse(time.RFC3339, first)
@@ -345,60 +345,22 @@ func TestDatetimeInterval(t *testing.T) {
 	ivalFirst := dtFirst.Interval(dtSecond)
 	ivalSecond := dtSecond.Interval(dtFirst)
 
-	expectedFirst := Interval{-2, -2, 0, 11, 0, 1, 0, 0, NoneAdjust}
-	expectedSecond := Interval{2, 2, 0, -11, 0, -1, 0, 0, NoneAdjust}
+	expectedFirst := Interval{-2, -2, 0, 11, 0, 61, 0, 0, NoneAdjust}
+	expectedSecond := Interval{2, 2, 0, -11, 0, -61, 0, 0, NoneAdjust}
 
 	if !reflect.DeepEqual(ivalFirst, expectedFirst) {
 		t.Errorf("Unexpected interval %v, expected %v", ivalFirst, expectedFirst)
 	}
 	if !reflect.DeepEqual(ivalSecond, expectedSecond) {
-		t.Errorf("Unexpected interval %v, expected %v", ivalFirst, expectedSecond)
+		t.Errorf("Unexpected interval %v, expected %v", ivalSecond, expectedSecond)
 	}
-}
-
-func TestDatetimeTarantoolInterval(t *testing.T) {
-	skipIfDatetimeUnsupported(t)
-
-	conn := test_helpers.ConnectWithValidation(t, server, opts)
-	defer conn.Close()
 
-	dates := []string{
-		"2015-03-20T17:50:56.000000009+01:00",
-		"2015-12-21T17:50:53Z",
-		"2010-02-24T23:03:56.0000013-04:00",
-		"1980-03-28T13:18:39.000099Z",
-		"2025-08-01T00:00:00.000000003+11:00",
-		"2020-01-01T01:01:01+11:30",
-	}
-	datetimes := []*Datetime{}
-	for _, date := range dates {
-		tm, err := time.Parse(time.RFC3339, date)
-		if err != nil {
-			t.Fatalf("Error in time.Parse(%s): %s", date, err)
-		}
-		dt, err := NewDatetime(tm)
-		if err != nil {
-			t.Fatalf("Error in NewDatetime(%s): %s", tm, err)
-		}
-		datetimes = append(datetimes, dt)
-	}
-
-	for _, dti := range datetimes {
-		for _, dtj := range datetimes {
-			t.Run(fmt.Sprintf("%s_to_%s", dti.ToTime(), dtj.ToTime()),
-				func(t *testing.T) {
-					resp, err := conn.Call17("call_datetime_interval",
-						[]interface{}{dti, dtj})
-					if err != nil {
-						t.Fatalf("Unable to call call_datetime_interval: %s", err)
-					}
-					ival := dti.Interval(dtj)
-					ret := resp.Data[0].(Interval)
-					if !reflect.DeepEqual(ival, ret) {
-						t.Fatalf("%v != %v", ival, ret)
-					}
-				})
-		}
+	dtFirst, err = dtFirst.Add(ivalFirst)
+	if err != nil {
+		t.Fatalf("Unable to add an intarval: %s", err)
+	}
+	if !dtFirst.ToTime().Equal(dtSecond.ToTime()) {
+		t.Errorf("Incorrect add interval result: %s, expected %s", dtFirst.ToTime(), dtSecond.ToTime())
 	}
 }