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Fixed Japanese Vernal and Autumnal Equinox days (#116)
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* Fixed Japanese Equinox Day calculation

There was an algorithm to calculate Vernal and Autumnal Equinox Days for Japanese calendar. Although specific days for these holidays are announced every year by the government, it has never announced a different date.

* Fixed Japanese Vernal and Autumnal Equinox days

Fixed case when Vernal or Autumnal Equinox day falls on Sunday. In this case the next Monday becomes a holiday.

---------

Co-authored-by: Mazov Sergey <mazov@indexpro.co.jp>
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@Makaopior
Makaopior and Mazov Sergey authored Mar 7, 2024
1 parent f17de33 commit 2decb8c
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Showing 2 changed files with 29 additions and 17 deletions.
36 changes: 24 additions & 12 deletions src/PublicHoliday/JapanPublicHoliday.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -58,26 +58,32 @@ public static DateTime VernalEquinoxDay(int year)

var yearModuloFour = year % 4;

DateTime vernalEquinoxDay;
if (year >= 1960 && year <= 1991)
{
return yearModuloFour == 0
vernalEquinoxDay = yearModuloFour == 0
? new DateTime(year, 3, 20)
: new DateTime(year, 3, 21);
}
if (year >= 1992 && year <= 2023)
else if (year >= 1992 && year <= 2023)
{
return yearModuloFour == 0 || yearModuloFour == 1
vernalEquinoxDay = yearModuloFour == 0 || yearModuloFour == 1
? new DateTime(year, 3, 20)
: new DateTime(year, 3, 21);
}
if (year >= 2024 && year <= 2055)
else if (year >= 2024 && year <= 2055)
{
return yearModuloFour == 3
vernalEquinoxDay = yearModuloFour == 3
? new DateTime(year, 3, 21)
: new DateTime(year, 3, 20);
}
else
{
// May be not precise
vernalEquinoxDay = new DateTime(year, 3, 20);
}

return FixSunday(new DateTime(year, 3, 20));
return FixSunday(vernalEquinoxDay);
}

/// <summary>
Expand Down Expand Up @@ -169,24 +175,30 @@ public static DateTime AutumnalEquinoxDay(int year)

var yearModuloFour = year % 4;

DateTime autumnalEquinoxDay;
if (year >= 1980 && year <= 2011)
{
return new DateTime(year, 9, 23);
autumnalEquinoxDay = new DateTime(year, 9, 23);
}
if (year >= 2012 && year <= 2043)
else if (year >= 2012 && year <= 2043)
{
return yearModuloFour == 0
autumnalEquinoxDay = yearModuloFour == 0
? new DateTime(year, 9, 22)
: new DateTime(year, 9, 23);
}
if (year >= 2044 && year <= 2075)
else if (year >= 2044 && year <= 2075)
{
return yearModuloFour == 0 || yearModuloFour == 1
autumnalEquinoxDay = yearModuloFour == 0 || yearModuloFour == 1
? new DateTime(year, 9, 22)
: new DateTime(year, 9, 23);
}
else
{
// May be not precise
autumnalEquinoxDay = new DateTime(year, 9, 23);
}

return FixSunday(new DateTime(year, 9, 23));
return FixSunday(autumnalEquinoxDay);
}

/// <summary>
Expand Down
10 changes: 5 additions & 5 deletions tests/PublicHolidayTests/TestJapanPublicHoliday.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ public void TestVernalEquinoxDay()
{
Assert.AreEqual(new DateTime(1980, 3, 20), JapanPublicHoliday.VernalEquinoxDay(1980));
Assert.AreEqual(new DateTime(1981, 3, 21), JapanPublicHoliday.VernalEquinoxDay(1981));
Assert.AreEqual(new DateTime(1982, 3, 21), JapanPublicHoliday.VernalEquinoxDay(1982));
Assert.AreEqual(new DateTime(1982, 3, 22), JapanPublicHoliday.VernalEquinoxDay(1982));
Assert.AreEqual(new DateTime(1983, 3, 21), JapanPublicHoliday.VernalEquinoxDay(1983));

Assert.AreEqual(new DateTime(2000, 3, 20), JapanPublicHoliday.VernalEquinoxDay(2000));
Expand All @@ -53,7 +53,7 @@ public void TestVernalEquinoxDay()
Assert.AreEqual(new DateTime(2024, 3, 20), JapanPublicHoliday.VernalEquinoxDay(2024));
Assert.AreEqual(new DateTime(2025, 3, 20), JapanPublicHoliday.VernalEquinoxDay(2025));
Assert.AreEqual(new DateTime(2026, 3, 20), JapanPublicHoliday.VernalEquinoxDay(2026));
Assert.AreEqual(new DateTime(2027, 3, 21), JapanPublicHoliday.VernalEquinoxDay(2027));
Assert.AreEqual(new DateTime(2027, 3, 22), JapanPublicHoliday.VernalEquinoxDay(2027));
}

[TestMethod]
Expand All @@ -65,7 +65,7 @@ public void TestAutumnalEquinoxDay()
Assert.AreEqual(new DateTime(1983, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(1983));

Assert.AreEqual(new DateTime(2000, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2000));
Assert.AreEqual(new DateTime(2001, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2001));
Assert.AreEqual(new DateTime(2001, 9, 24), JapanPublicHoliday.AutumnalEquinoxDay(2001));
Assert.AreEqual(new DateTime(2002, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2002));
Assert.AreEqual(new DateTime(2003, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2003));

Expand All @@ -74,14 +74,14 @@ public void TestAutumnalEquinoxDay()
Assert.AreEqual(new DateTime(2022, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2022));
Assert.AreEqual(new DateTime(2023, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2023));

Assert.AreEqual(new DateTime(2024, 9, 22), JapanPublicHoliday.AutumnalEquinoxDay(2024));
Assert.AreEqual(new DateTime(2024, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2024));
Assert.AreEqual(new DateTime(2025, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2025));
Assert.AreEqual(new DateTime(2026, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2026));
Assert.AreEqual(new DateTime(2027, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2027));

Assert.AreEqual(new DateTime(2044, 9, 22), JapanPublicHoliday.AutumnalEquinoxDay(2044));
Assert.AreEqual(new DateTime(2045, 9, 22), JapanPublicHoliday.AutumnalEquinoxDay(2045));
Assert.AreEqual(new DateTime(2046, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2046));
Assert.AreEqual(new DateTime(2046, 9, 24), JapanPublicHoliday.AutumnalEquinoxDay(2046));
Assert.AreEqual(new DateTime(2047, 9, 23), JapanPublicHoliday.AutumnalEquinoxDay(2047));
}

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