Merge branch 'develop'

# Conflicts:
#	README.md
#	calendar.go
#	calendar/lunar/lunar.go
#	calendar_unit_test.go

Author: kuafuRace

README.cn.md

@@ -1360,7 +1360,8 @@ fmt.Printf("%d", person.Field8) // 1596604455999999999
 
 目前支持的日历有
 
-* [中国农历](./calendar/lunar/README.cn.md "中国农历"): 由 [gouguoyin](https://github.com/gouguoyin "gouguoyin") 贡献
+* [中国农历](./calendar/lunar/README.cn.md "中国农历")
+* [儒略日/简化儒略日](./calendar/julian/README.cn.md "儒略日/简化儒略日")
 
 ##### 国际化
 

README.jp.md

@@ -1360,7 +1360,8 @@ fmt.Printf("%d", person.Field8) // 1596604455999999999
 
 現在サポートされているカレンダーは
 
-* [中国の旧暦](./calendar/lunar/README.jp.md "中国の旧暦"): [gouguoyin](https://github.com/gouguoyin "gouguoyin") による貢献
+* [中国の旧暦](./calendar/lunar/README.jp.md "中国の旧暦")
+* [儒略の日/簡略化儒略の日](./calendar/julian/README.jp.md "儒略日/简化儒略日")
 
 ##### 国際化
 

README.md

@@ -1355,10 +1355,9 @@ fmt.Printf("%d", person.Field8) // 1596604455999999999
 
 The following calendars are supported
 
-* [Chinese Lunar](./calendar/lunar/README.md "Chinese Lunar")：contributed
-  by [gouguoyin](https://github.com/gouguoyin "gouguoyin")
-* [Vietnamese Lunar](./calendar/vlunar/README.md "Vietnamese Lunar")：contributed
-  by [culy247](https://github.com/culy247 "culy247")
+* [Chinese Lunar](./calendar/lunar/README.md "Chinese Lunar")
+* [Julian Day/Modified Julian Day](./calendar/julian/README.md "JD/MJD")
+
 ##### I18n
 
 The following languages are supported

calendar.go

@@ -1,12 +1,12 @@
 package carbon
 
 import (
+	"github.com/golang-module/carbon/v2/calendar/julian"
 	"github.com/golang-module/carbon/v2/calendar/lunar"
-	"github.com/golang-module/carbon/v2/calendar/vlunar"
 )
 
 // Lunar converts gregorian calendar to lunar calendar.
-// 将 公历 转为 农历
+// 将 公历 转化为 农历
 func (c Carbon) Lunar() (l lunar.Lunar) {
 	if c.Error != nil {
 		l.Error = c.Error
@@ -23,20 +23,19 @@ func CreateFromLunar(year, month, day, hour, minute, second int, isLeapMonth boo
 	return c
 }
 
-// Lunar converts the solar calendar to the lunar calendar.
-// 将公历转为农历
-func (c Carbon) VLunar() (l vlunar.Lunar) {
+// Julian converts gregorian calendar to Julian calendar
+// 将 公历 转化为 儒略历
+func (c Carbon) Julian() (j julian.Julian) {
 	if c.Error != nil {
-		l.Error = c.Error
-		return l
+		return j
 	}
-	return vlunar.NewGregorian(c.ToStdTime()).ToLunar()
+	return julian.NewGregorian(c.ToStdTime()).ToJulian()
 }
 
-// CreateFromLunar creates a Carbon instance from Lunar date and time.
-// 从 农历日期 创建 Carbon 实例
-func CreateFromVLunar(year, month, day, hour, minute, second int, isLeapMonth bool) Carbon {
+// CreateFromJulian creates a Carbon instance from Julian Day.or Modified Julian Day
+// 从 儒略日/简化儒略日 创建 Carbon 实例
+func CreateFromJulian(f float64) Carbon {
 	c := NewCarbon()
-	c.time = vlunar.NewLunar(year, month, day, hour, minute, second, isLeapMonth).ToGregorian().Time
+	c.time = julian.NewJulian(f).ToGregorian().Time
 	return c
 }

calendar/gregorian.go

@@ -128,6 +128,8 @@ func NewGregorian(t time.Time) (g Gregorian) {
 	return g
 }
 
+// Date gets gregorian year, month, and day like 2020, 8, 5.
+// 获取公历年、月、日
 func (g Gregorian) Date() (year, month, day int) {
 	if g.IsZero() {
 		return 0, 0, 0
@@ -138,66 +140,99 @@ func (g Gregorian) Date() (year, month, day int) {
 	return
 }
 
+// Clock gets gregorian hour, minute, and second like 13, 14, 15.
+// 获取公历时、分、秒
 func (g Gregorian) Clock() (hour, minute, second int) {
 	if g.IsZero() {
 		return 0, 0, 0
 	}
 	return g.Time.Clock()
 }
 
+// Year gets gregorian year like 2020.
+// 获取公历年
 func (g Gregorian) Year() int {
 	if g.IsZero() {
 		return 0
 	}
 	return g.Time.Year()
 }
 
+// Month gets gregorian month like 8.
+// 获取公历月
 func (g Gregorian) Month() int {
 	if g.IsZero() {
 		return 0
 	}
 	return int(g.Time.Month())
 }
 
+// Day gets gregorian day like 5.
+// 获取公历日
 func (g Gregorian) Day() int {
 	if g.IsZero() {
 		return 0
 	}
 	return g.Time.Day()
 }
 
+// Hour gets gregorian hour like 13.
+// 获取公历小时
 func (g Gregorian) Hour() int {
 	if g.IsZero() {
 		return 0
 	}
 	return g.Time.Hour()
 }
 
+// Minute gets gregorian minute like 14.
+// 获取公历分钟数
 func (g Gregorian) Minute() int {
 	if g.IsZero() {
 		return 0
 	}
 	return g.Time.Minute()
 }
 
+// Second gets gregorian second like 15.
+// 获取公历秒数
 func (g Gregorian) Second() int {
 	if g.IsZero() {
 		return 0
 	}
 	return g.Time.Second()
 }
 
+// Location gets gregorian timezone information.
+// 获取时区信息
 func (g Gregorian) Location() *time.Location {
 	return g.Time.Location()
 }
 
+// String implements the interface Stringer for Gregorian struct.
+// 实现 Stringer 接口
 func (g Gregorian) String() string {
 	if g.IsZero() {
 		return ""
 	}
 	return g.Time.Format(DateTimeLayout)
 }
 
+// IsZero reports whether is zero time.
+// 是否是零值时间
 func (g Gregorian) IsZero() bool {
 	return g.Time.IsZero()
 }
+
+// IsLeapYear reports whether is a leap year.
+// 是否是闰年
+func (g Gregorian) IsLeapYear() bool {
+	if g.IsZero() {
+		return false
+	}
+	year := g.Year()
+	if year%400 == 0 || (year%4 == 0 && year%100 != 0) {
+		return true
+	}
+	return false
+}