Change Chanukah candle-lighting time from dusk to bein hashmashos,

courtesy @MaxBGreenberg. bein hashmashos is 13.5 minutes before solar depression of 7.083 degrees (#10)
hebcal · Jan 30, 2024 · e5c3279 · e5c3279
1 parent 50cb48d
commit e5c3279
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Showing 4 changed files with 27 additions and 33 deletions.
diff --git a/hebcal/candles.go b/hebcal/candles.go
@@ -47,7 +47,7 @@ type TimedEvent struct {
 
 func NewTimedEvent(hd hdate.HDate, desc string, flags event.HolidayFlags, t time.Time,
 	sunsetOffset int, linkedEvent event.CalEvent, opts *CalOptions) TimedEvent {
-	if (t == time.Time{}) {
+	if t.IsZero() {
 		return TimedEvent{}
 	}
 	var emoji string
@@ -136,7 +136,7 @@ func makeCandleEvent(hd hdate.HDate, opts *CalOptions, ev event.CalEvent) TimedE
 	} else {
 		eventTime = z.Tzeit(opts.HavdalahDeg)
 	}
-	if (eventTime == time.Time{}) {
+	if eventTime.IsZero() {
 		return TimedEvent{} // no sunset
 	}
 	desc := "Candle lighting"
@@ -162,8 +162,8 @@ func makeChanukahCandleLighting(ev event.HolidayEvent, opts *CalOptions) TimedEv
 	year, month, day := hd.Greg()
 	gregDate := time.Date(year, month, day, 0, 0, 0, 0, time.UTC)
 	z := zmanim.New(loc, gregDate)
-	candleLightingTime := z.Dusk()
-	if (candleLightingTime == time.Time{}) {
+	candleLightingTime := z.BeinHashmashos()
+	if candleLightingTime.IsZero() {
 		return TimedEvent{} // no sunset
 	}
 	return TimedEvent{

diff --git a/hebcal/hebcal_test.go b/hebcal/hebcal_test.go
@@ -176,18 +176,18 @@ func TestHebrewCalendarChanukahCandles(t *testing.T) {
 	assert.Equal(nil, err)
 	assert.Equal(14, len(events))
 	expected := []string{
-		"2022-12-18 Chanukah: 1 Candle: 5:04",
-		"2022-12-19 Chanukah: 2 Candles: 5:05",
-		"2022-12-20 Chanukah: 3 Candles: 5:05",
-		"2022-12-21 Chanukah: 4 Candles: 5:06",
-		"2022-12-22 Chanukah: 5 Candles: 5:06",
+		"2022-12-18 Chanukah: 1 Candle: 4:56",
+		"2022-12-19 Chanukah: 2 Candles: 4:57",
+		"2022-12-20 Chanukah: 3 Candles: 4:57",
+		"2022-12-21 Chanukah: 4 Candles: 4:58",
+		"2022-12-22 Chanukah: 5 Candles: 4:58",
 		"2022-12-23 Chanukah: 6 Candles: 4:00",
 		"2022-12-23 Candle lighting: 4:00",
 		"2022-12-24 Chag HaBanot",
 		"2022-12-24 Chanukah: 7 Candles: 5:20",
 		"2022-12-24 Rosh Chodesh Tevet",
 		"2022-12-24 Havdalah: 5:20",
-		"2022-12-25 Chanukah: 8 Candles: 5:08",
+		"2022-12-25 Chanukah: 8 Candles: 5:00",
 		"2022-12-25 Rosh Chodesh Tevet",
 		"2022-12-26 Chanukah: 8th Day",
 	}
@@ -557,5 +557,5 @@ func TestHebrewCalendarZmanimOnly(t *testing.T) {
 	}
 	events, err := hebcal.HebrewCalendar(&opts)
 	assert.Equal(nil, err)
-	assert.Equal(15, len(events)) // not 16 (no Alot HaShachar)
+	assert.Equal(14, len(events)) // not 15 (no Alot HaShachar)
 }
diff --git a/zmanim/zmanim.go b/zmanim/zmanim.go
@@ -59,10 +59,8 @@ func New(location *Location, date time.Time) Zmanim {
 	return Zmanim{Location: location, Year: year, Month: month, Day: day, loc: loc}
 }
 
-var nilTime = time.Time{}
-
 func (z *Zmanim) inLoc(dt time.Time) time.Time {
-	if dt == nilTime {
+	if dt.IsZero() {
 		return dt
 	}
 	return dt.In(z.loc)
@@ -229,15 +227,20 @@ func (z *Zmanim) Tzeit(angle float64) time.Time {
 	return z.timeAtAngle(angle, false)
 }
 
+const ThirteenFive time.Duration = -1 * time.Duration(13.5*float64(time.Minute))
+
 // Rabbeinu Tam holds that bein hashmashos is a specific time between sunset and tzeis hakochavim
 // One opinion on how to calculate this time is that it is 13.5 minutes before tzies 7.083
 func (z *Zmanim) BeinHashmashos() time.Time {
-	tzeis:=z.Tzeit(Tzeit3MediumStars)
-	return tzeis.Add(-time.Duration(13.5 * float64(time.Minute)))
+	tzeis := z.Tzeit(Tzeit3MediumStars)
+	if tzeis.IsZero() {
+		return tzeis
+	}
+	return tzeis.Add(ThirteenFive)
 }
 
 func (z *Zmanim) riseSetOffset(t time.Time, offset int, roundTime bool) time.Time {
-	if t == nilTime {
+	if t.IsZero() {
 		return t
 	}
 	year, month, day := t.Date()

diff --git a/zmanim/zmanim_test.go b/zmanim/zmanim_test.go
@@ -20,7 +20,6 @@ func TestZmanimChicago(t *testing.T) {
 		"Fri, 05 Jun 2020 03:25:34 -0500",
 		"Fri, 05 Jun 2020 04:03:11 -0500",
 		"Fri, 05 Jun 2020 04:12:55 -0500",
-		"Fri, 05 Jun 2020 04:42:37 -0500",
 		"Fri, 05 Jun 2020 05:16:28 -0500",
 		"Fri, 05 Jun 2020 09:02:54 -0500",
 		"Fri, 05 Jun 2020 08:26:54 -0500",
@@ -31,7 +30,8 @@ func TestZmanimChicago(t *testing.T) {
 		"Fri, 05 Jun 2020 17:13:32 -0500",
 		"Fri, 05 Jun 2020 18:47:53 -0500",
 		"Fri, 05 Jun 2020 20:22:15 -0500",
-		"Fri, 05 Jun 2020 20:56:06 -0500",
+		"Fri, 05 Jun 2020 20:50:02 -0500",
+		"Fri, 05 Jun 2020 21:03:32 -0500",
 		"Fri, 05 Jun 2020 21:13:28 -0500",
 	}
 	times := []time.Time{
@@ -51,6 +51,7 @@ func TestZmanimChicago(t *testing.T) {
 		zman.PlagHaMincha(),
 		zman.Sunset(),
 		zman.BeinHashmashos(),
+		zman.Tzeit(7.083),
 		zman.Tzeit(8.5),
 	}
 	actual := make([]string, 18)
@@ -74,7 +75,6 @@ func TestZmanimTelAviv(t *testing.T) {
 		"Sat, 06 Mar 2021 04:50:19 +0200",
 		"Sat, 06 Mar 2021 05:12:02 +0200",
 		"Sat, 06 Mar 2021 05:18:11 +0200",
-		"Sat, 06 Mar 2021 05:38:01 +0200",
 		"Sat, 06 Mar 2021 06:02:30 +0200",
 		"Sat, 06 Mar 2021 08:57:23 +0200",
 		"Sat, 06 Mar 2021 08:21:23 +0200",
@@ -85,7 +85,8 @@ func TestZmanimTelAviv(t *testing.T) {
 		"Sat, 06 Mar 2021 15:16:20 +0200",
 		"Sat, 06 Mar 2021 16:29:12 +0200",
 		"Sat, 06 Mar 2021 17:42:05 +0200",
-		"Sat, 06 Mar 2021 18:06:34 +0200",
+		"Sat, 06 Mar 2021 17:58:11 +0200",
+		"Sat, 06 Mar 2021 18:11:41 +0200",
 		"Sat, 06 Mar 2021 18:18:23 +0200",
 	}
 	times := []time.Time{
@@ -94,7 +95,6 @@ func TestZmanimTelAviv(t *testing.T) {
 		zman.AlotHaShachar(),
 		zman.Misheyakir(),
 		zman.MisheyakirMachmir(),
-		zman.Dawn(),
 		zman.Sunrise(),
 		zman.SofZmanShma(),
 		zman.SofZmanShmaMGA(),
@@ -105,8 +105,8 @@ func TestZmanimTelAviv(t *testing.T) {
 		zman.MinchaKetana(),
 		zman.PlagHaMincha(),
 		zman.Sunset(),
-		zman.Dusk(),
 		zman.BeinHashmashos(),
+		zman.Tzeit(7.083),
 		zman.Tzeit(8.5),
 	}
 	actual := make([]string, 18)
@@ -145,7 +145,7 @@ func TestZmanimHelsinki(t *testing.T) {
 		} else {
 			t = zman.Tzeit(8.5)
 		}
-		if (t == time.Time{}) {
+		if t.IsZero() {
 			actual[idx] = "undefined"
 		} else {
 			actual[idx] = t.Format(time.RFC1123Z)
@@ -177,15 +177,6 @@ func ExampleZmanim_SunsetOffset() {
 	// 2020-06-05 21:12:00 -0500 CDT
 }
 
-func ExampleZmanim_Dusk() {
-	dt := time.Date(2022, time.December, 24, 12, 0, 0, 0, time.UTC)
-	location := zmanim.NewLocation("Amund Ringnes Island", "CA", 78.305499, -96.917471, "America/Regina")
-	zman := zmanim.New(&location, dt)
-	dusk := zman.Dusk()
-	fmt.Println(dusk)
-	// Output: 0001-01-01 00:00:00 +0000 UTC
-}
-
 func TestZmanimAmsterdam(t *testing.T) {
 	assert := assert.New(t)
 	dt := time.Date(2023, time.May, 29, 12, 0, 0, 0, time.UTC)