diff --git a/README.cn.md b/README.cn.md
index ca2f1ff0..2eb8f039 100644
--- a/README.cn.md
+++ b/README.cn.md
@@ -913,6 +913,7 @@ fmt.Sprintf("%s", carbon.Parse("2020-08-05 13:14:15")) // 2020-08-05 13:14:15
 carbon.Parse("2020-08-05 13:14:15").ToString() // 2020-08-05 13:14:15.999999 +0800 CST
 
 // 输出指定布局的字符串,Layout()是ToLayoutString()的简写
+carbon.Parse("2020-08-05 13:14:15").Layout(carbon.ISO8601Layout) // 2020-08-05T13:14:15+08:00
 carbon.Parse("2020-08-05 13:14:15").Layout("20060102150405") // 20200805131415
 carbon.Parse("2020-08-05 13:14:15").Layout("2006年01月02日 15时04分05秒") // 2020年08月05日 13时14分15秒
 carbon.Parse("2020-08-05 13:14:15").Layout("It is 2006-01-02 15:04:05") // It is 2020-08-05 13:14:15
diff --git a/README.jp.md b/README.jp.md
index 2d659a8a..1cbda38e 100644
--- a/README.jp.md
+++ b/README.jp.md
@@ -909,6 +909,7 @@ fmt.Sprintf("%s", carbon.Parse("2020-08-05 13:14:15")) // 2020-08-05 13:14:15
 carbon.Parse("2020-08-05 13:14:15").ToString() // 2020-08-05 13:14:15.999999 +0800 CST
 
 // レイアウトを指定する文字列を出力, Layout() は 是ToLayoutString() の略記です
+carbon.Parse("2020-08-05 13:14:15").Layout(carbon.ISO8601Layout) // 2020-08-05T13:14:15+08:00
 carbon.Parse("2020-08-05 13:14:15").Layout("20060102150405") // 20200805131415
 carbon.Parse("2020-08-05 13:14:15").Layout("2006年01月02日 15时04分05秒") // 2020年08月05日 13时14分15秒
 carbon.Parse("2020-08-05 13:14:15").Layout("It is 2006-01-02 15:04:05") // It is 2020-08-05 13:14:15
diff --git a/README.md b/README.md
index 00095ce6..8c80c4e0 100644
--- a/README.md
+++ b/README.md
@@ -908,6 +908,7 @@ fmt.Sprintf("%s", carbon.Parse("2020-08-05 13:14:15")) // 2020-08-05 13:14:15
 carbon.Parse("2020-08-05 13:14:15").ToString() // 2020-08-05 13:14:15.999999 +0800 CST
 
 // Output a string by layout, Layout() is shorthand for ToLayoutString()
+carbon.Parse("2020-08-05 13:14:15").Layout(carbon.ISO8601Layout) // 2020-08-05T13:14:15+08:00
 carbon.Parse("2020-08-05 13:14:15").Layout("20060102150405") // 20200805131415
 carbon.Parse("2020-08-05 13:14:15").Layout("2006年01月02日 15时04分05秒") // 2020年08月05日 13时14分15秒
 carbon.Parse("2020-08-05 13:14:15").Layout("It is 2006-01-02 15:04:05") // It is 2020-08-05 13:14:15
diff --git a/carbon.go b/carbon.go
index 5b2f120a..351e221c 100644
--- a/carbon.go
+++ b/carbon.go
@@ -122,44 +122,44 @@ const (
 	SecondsPerMinute   = 60     // 每分钟60秒
 )
 
-// formats constant
-// 时间格式化常量
+// layouts constant
+// 时间布局常量
 const (
-	ANSICFormat              = time.ANSIC
-	UnixDateFormat           = time.UnixDate
-	RubyDateFormat           = time.RubyDate
-	RFC822Format             = time.RFC822
-	RFC822ZFormat            = time.RFC822Z
-	RFC850Format             = time.RFC850
-	RFC1123Format            = time.RFC1123
-	RFC1123ZFormat           = time.RFC1123Z
-	RssFormat                = time.RFC1123Z
-	KitchenFormat            = time.Kitchen
-	RFC2822Format            = time.RFC1123Z
-	CookieFormat             = "Monday, 02-Jan-2006 15:04:05 MST"
-	RFC3339Format            = "2006-01-02T15:04:05Z07:00"
-	RFC3339MilliFormat       = "2006-01-02T15:04:05.999Z07:00"
-	RFC3339MicroFormat       = "2006-01-02T15:04:05.999999Z07:00"
-	RFC3339NanoFormat        = "2006-01-02T15:04:05.999999999Z07:00"
-	ISO8601Format            = "2006-01-02T15:04:05-07:00"
-	ISO8601MilliFormat       = "2006-01-02T15:04:05.999-07:00"
-	ISO8601MicroFormat       = "2006-01-02T15:04:05.999999-07:00"
-	ISO8601NanoFormat        = "2006-01-02T15:04:05.999999999-07:00"
-	RFC1036Format            = "Mon, 02 Jan 06 15:04:05 -0700"
-	RFC7231Format            = "Mon, 02 Jan 2006 15:04:05 GMT"
-	DayDateTimeFormat        = "Mon, Jan 2, 2006 3:04 PM"
-	DateTimeFormat           = "2006-01-02 15:04:05"
-	DateTimeMilliFormat      = "2006-01-02 15:04:05.999"
-	DateTimeMicroFormat      = "2006-01-02 15:04:05.999999"
-	DateTimeNanoFormat       = "2006-01-02 15:04:05.999999999"
-	DateFormat               = "2006-01-02"
-	TimeFormat               = "15:04:05"
-	ShortDateTimeFormat      = "20060102150405"
-	ShortDateTimeMilliFormat = "20060102150405.999"
-	ShortDateTimeMicroFormat = "20060102150405.999999"
-	ShortDateTimeNanoFormat  = "20060102150405.999999999"
-	ShortDateFormat          = "20060102"
-	ShortTimeFormat          = "150405"
+	ANSICLayout              = time.ANSIC
+	UnixDateLayout           = time.UnixDate
+	RubyDateLayout           = time.RubyDate
+	RFC822Layout             = time.RFC822
+	RFC822ZLayout            = time.RFC822Z
+	RFC850Layout             = time.RFC850
+	RFC1123Layout            = time.RFC1123
+	RFC1123ZLayout           = time.RFC1123Z
+	RssLayout                = time.RFC1123Z
+	KitchenLayout            = time.Kitchen
+	RFC2822Layout            = time.RFC1123Z
+	CookieLayout             = "Monday, 02-Jan-2006 15:04:05 MST"
+	RFC3339Layout            = "2006-01-02T15:04:05Z07:00"
+	RFC3339MilliLayout       = "2006-01-02T15:04:05.999Z07:00"
+	RFC3339MicroLayout       = "2006-01-02T15:04:05.999999Z07:00"
+	RFC3339NanoLayout        = "2006-01-02T15:04:05.999999999Z07:00"
+	ISO8601Layout            = "2006-01-02T15:04:05-07:00"
+	ISO8601MilliLayout       = "2006-01-02T15:04:05.999-07:00"
+	ISO8601MicroLayout       = "2006-01-02T15:04:05.999999-07:00"
+	ISO8601NanoLayout        = "2006-01-02T15:04:05.999999999-07:00"
+	RFC1036Layout            = "Mon, 02 Jan 06 15:04:05 -0700"
+	RFC7231Layout            = "Mon, 02 Jan 2006 15:04:05 GMT"
+	DayDateTimeLayout        = "Mon, Jan 2, 2006 3:04 PM"
+	DateTimeLayout           = "2006-01-02 15:04:05"
+	DateTimeMilliLayout      = "2006-01-02 15:04:05.999"
+	DateTimeMicroLayout      = "2006-01-02 15:04:05.999999"
+	DateTimeNanoLayout       = "2006-01-02 15:04:05.999999999"
+	DateLayout               = "2006-01-02"
+	TimeLayout               = "15:04:05"
+	ShortDateTimeLayout      = "20060102150405"
+	ShortDateTimeMilliLayout = "20060102150405.999"
+	ShortDateTimeMicroLayout = "20060102150405.999999"
+	ShortDateTimeNanoLayout  = "20060102150405.999999999"
+	ShortDateLayout          = "20060102"
+	ShortTimeLayout          = "150405"
 )
 
 // Carbon defines a Carbon struct.
@@ -222,9 +222,9 @@ func (c Carbon) Tomorrow(timezone ...string) Carbon {
 	}
 	if c.IsZero() {
 		c.time = c.Now().Carbon2Time().AddDate(0, 0, 1)
-	} else {
-		c.time = c.Carbon2Time().AddDate(0, 0, 1)
+		return c
 	}
+	c.time = c.Carbon2Time().AddDate(0, 0, 1)
 	return c
 }
 
@@ -245,9 +245,9 @@ func (c Carbon) Yesterday(timezone ...string) Carbon {
 	}
 	if c.IsZero() {
 		c.time = c.Now().Carbon2Time().AddDate(0, 0, -1)
-	} else {
-		c.time = c.Carbon2Time().AddDate(0, 0, -1)
+		return c
 	}
+	c.time = c.Carbon2Time().AddDate(0, 0, -1)
 	return c
 }
 
diff --git a/carbon_test.go b/carbon_test.go
index 03917521..2ba372cd 100755
--- a/carbon_test.go
+++ b/carbon_test.go
@@ -11,11 +11,11 @@ func TestCarbon_Now(t *testing.T) {
 	assert := assert.New(t)
 
 	actual1 := Now().ToDateString()
-	expected1 := time.Now().Format(DateFormat)
+	expected1 := time.Now().Format(DateLayout)
 	assert.Equal(expected1, actual1)
 
 	actual2 := Now(Local).ToDateString()
-	expected2 := time.Now().In(time.Local).Format(DateFormat)
+	expected2 := time.Now().In(time.Local).Format(DateLayout)
 	assert.Equal(expected2, actual2)
 }
 
@@ -23,12 +23,12 @@ func TestCarbon_Yesterday(t *testing.T) {
 	assert := assert.New(t)
 
 	c1 := Yesterday()
-	expected1 := time.Now().AddDate(0, 0, -1).Format(DateFormat)
+	expected1 := time.Now().AddDate(0, 0, -1).Format(DateLayout)
 	assert.Nil(c1.Error)
 	assert.Equal(expected1, c1.ToDateString())
 
 	c2 := Yesterday(Local)
-	expected2 := time.Now().In(time.Local).AddDate(0, 0, -1).Format(DateFormat)
+	expected2 := time.Now().In(time.Local).AddDate(0, 0, -1).Format(DateLayout)
 	assert.Nil(c2.Error)
 	assert.Equal(expected2, c2.ToDateString())
 
@@ -41,12 +41,12 @@ func TestCarbon_Tomorrow(t *testing.T) {
 	assert := assert.New(t)
 
 	c1 := Tomorrow()
-	expected1 := time.Now().AddDate(0, 0, 1).Format(DateFormat)
+	expected1 := time.Now().AddDate(0, 0, 1).Format(DateLayout)
 	assert.Nil(c1.Error)
 	assert.Equal(expected1, c1.ToDateString())
 
 	c2 := Tomorrow(Local)
-	expected2 := time.Now().In(time.Local).AddDate(0, 0, 1).Format(DateFormat)
+	expected2 := time.Now().In(time.Local).AddDate(0, 0, 1).Format(DateLayout)
 	assert.Nil(c2.Error)
 	assert.Equal(expected2, c2.ToDateString())
 
@@ -58,7 +58,7 @@ func TestCarbon_Tomorrow(t *testing.T) {
 func TestCarbon_Time2Carbon(t *testing.T) {
 	assert := assert.New(t)
 
-	expected := time.Now().Format(DateTimeFormat)
+	expected := time.Now().Format(DateTimeLayout)
 	actual := Time2Carbon(time.Now()).ToDateTimeString()
 	assert.Equal(expected, actual)
 }
@@ -66,8 +66,8 @@ func TestCarbon_Time2Carbon(t *testing.T) {
 func TestCarbon_Carbon2Time(t *testing.T) {
 	assert := assert.New(t)
 
-	expected := time.Now().Format(DateTimeFormat)
-	actual := Now().Carbon2Time().Format(DateTimeFormat)
+	expected := time.Now().Format(DateTimeLayout)
+	actual := Now().Carbon2Time().Format(DateTimeLayout)
 	assert.Equal(expected, actual)
 }
 
diff --git a/outputer.go b/outputer.go
index 25b9cf68..cca2196f 100644
--- a/outputer.go
+++ b/outputer.go
@@ -12,7 +12,7 @@ func (c Carbon) String() string {
 	return c.ToDateTimeString()
 }
 
-// ToString outputs a string in "2006-01-02 15:04:05.999999999 -0700 MST" format.
+// ToString outputs a string in "2006-01-02 15:04:05.999999999 -0700 MST" layout.
 // 输出 "2006-01-02 15:04:05.999999999 -0700 MST" 格式字符串
 func (c Carbon) ToString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -24,7 +24,7 @@ func (c Carbon) ToString(timezone ...string) string {
 	return c.Carbon2Time().String()
 }
 
-// ToMonthString outputs a string in month format like "January", i18n is supported.
+// ToMonthString outputs a string in month layout like "January", i18n is supported.
 // 输出完整月份字符串，支持i18n
 func (c Carbon) ToMonthString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -45,7 +45,7 @@ func (c Carbon) ToMonthString(timezone ...string) string {
 	return ""
 }
 
-// ToShortMonthString outputs a string in short month format like "Jan", i18n is supported.
+// ToShortMonthString outputs a string in short month layout like "Jan", i18n is supported.
 // 输出缩写月份字符串，支持i18n
 func (c Carbon) ToShortMonthString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -66,7 +66,7 @@ func (c Carbon) ToShortMonthString(timezone ...string) string {
 	return ""
 }
 
-// ToWeekString outputs a string in week format like "Sunday", i18n is supported.
+// ToWeekString outputs a string in week layout like "Sunday", i18n is supported.
 // 输出完整星期字符串，支持i18n
 func (c Carbon) ToWeekString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -87,7 +87,7 @@ func (c Carbon) ToWeekString(timezone ...string) string {
 	return ""
 }
 
-// ToShortWeekString outputs a string in short week format like "Sun", i18n is supported.
+// ToShortWeekString outputs a string in short week layout like "Sun", i18n is supported.
 // 输出缩写星期字符串，支持i18n
 func (c Carbon) ToShortWeekString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -108,7 +108,7 @@ func (c Carbon) ToShortWeekString(timezone ...string) string {
 	return ""
 }
 
-// ToDayDateTimeString outputs a string in "Mon, Jan 2, 2006 3:04 PM" format.
+// ToDayDateTimeString outputs a string in "Mon, Jan 2, 2006 3:04 PM" layout.
 // 输出 "Mon, Jan 2, 2006 3:04 PM" 格式字符串
 func (c Carbon) ToDayDateTimeString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -117,10 +117,10 @@ func (c Carbon) ToDayDateTimeString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(DayDateTimeFormat)
+	return c.Carbon2Time().Format(DayDateTimeLayout)
 }
 
-// ToDateTimeString outputs a string in "2006-01-02 15:04:05" format.
+// ToDateTimeString outputs a string in "2006-01-02 15:04:05" layout.
 // 输出 "2006-01-02 15:04:05" 格式字符串
 func (c Carbon) ToDateTimeString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -129,10 +129,10 @@ func (c Carbon) ToDateTimeString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(DateTimeFormat)
+	return c.Carbon2Time().Format(DateTimeLayout)
 }
 
-// ToDateTimeMilliString outputs a string in "2006-01-02 15:04:05.999" format.
+// ToDateTimeMilliString outputs a string in "2006-01-02 15:04:05.999" layout.
 // 输出 "2006-01-02 15:04:05.999" 格式字符串
 func (c Carbon) ToDateTimeMilliString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -141,10 +141,10 @@ func (c Carbon) ToDateTimeMilliString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(DateTimeMilliFormat)
+	return c.Carbon2Time().Format(DateTimeMilliLayout)
 }
 
-// ToDateTimeMicroString outputs a string in "2006-01-02 15:04:05.999999" format.
+// ToDateTimeMicroString outputs a string in "2006-01-02 15:04:05.999999" layout.
 // 输出 "2006-01-02 15:04:05.999999" 格式字符串
 func (c Carbon) ToDateTimeMicroString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -153,10 +153,10 @@ func (c Carbon) ToDateTimeMicroString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(DateTimeMicroFormat)
+	return c.Carbon2Time().Format(DateTimeMicroLayout)
 }
 
-// ToDateTimeNanoString outputs a string in "2006-01-02 15:04:05.999999999" format.
+// ToDateTimeNanoString outputs a string in "2006-01-02 15:04:05.999999999" layout.
 // 输出 "2006-01-02 15:04:05.999999999" 格式字符串
 func (c Carbon) ToDateTimeNanoString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -165,10 +165,10 @@ func (c Carbon) ToDateTimeNanoString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(DateTimeNanoFormat)
+	return c.Carbon2Time().Format(DateTimeNanoLayout)
 }
 
-// ToShortDateTimeString outputs a string in "20060102150405" format.
+// ToShortDateTimeString outputs a string in "20060102150405" layout.
 // 输出 "20060102150405" 格式字符串
 func (c Carbon) ToShortDateTimeString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -177,10 +177,10 @@ func (c Carbon) ToShortDateTimeString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ShortDateTimeFormat)
+	return c.Carbon2Time().Format(ShortDateTimeLayout)
 }
 
-// ToShortDateTimeMilliString outputs a string in "20060102150405.999" format.
+// ToShortDateTimeMilliString outputs a string in "20060102150405.999" layout.
 // 输出 "20060102150405.999" 格式字符串
 func (c Carbon) ToShortDateTimeMilliString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -189,10 +189,10 @@ func (c Carbon) ToShortDateTimeMilliString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ShortDateTimeMilliFormat)
+	return c.Carbon2Time().Format(ShortDateTimeMilliLayout)
 }
 
-// ToShortDateTimeMicroString outputs a string in "20060102150405.999999" format.
+// ToShortDateTimeMicroString outputs a string in "20060102150405.999999" layout.
 // 输出 "20060102150405.999999" 格式字符串
 func (c Carbon) ToShortDateTimeMicroString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -201,10 +201,10 @@ func (c Carbon) ToShortDateTimeMicroString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ShortDateTimeMicroFormat)
+	return c.Carbon2Time().Format(ShortDateTimeMicroLayout)
 }
 
-// ToShortDateTimeNanoString outputs a string in "20060102150405.999999999" format.
+// ToShortDateTimeNanoString outputs a string in "20060102150405.999999999" layout.
 // 输出 "20060102150405.999999999" 格式字符串
 func (c Carbon) ToShortDateTimeNanoString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -213,10 +213,10 @@ func (c Carbon) ToShortDateTimeNanoString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ShortDateTimeNanoFormat)
+	return c.Carbon2Time().Format(ShortDateTimeNanoLayout)
 }
 
-// ToDateString outputs a string in "2006-01-02" format.
+// ToDateString outputs a string in "2006-01-02" layout.
 // 输出 "2006-01-02" 格式字符串
 func (c Carbon) ToDateString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -225,10 +225,10 @@ func (c Carbon) ToDateString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(DateFormat)
+	return c.Carbon2Time().Format(DateLayout)
 }
 
-// ToShortDateString outputs a string in "20060102" format.
+// ToShortDateString outputs a string in "20060102" layout.
 // 输出 "20060102" 格式字符串
 func (c Carbon) ToShortDateString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -237,10 +237,10 @@ func (c Carbon) ToShortDateString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ShortDateFormat)
+	return c.Carbon2Time().Format(ShortDateLayout)
 }
 
-// ToTimeString outputs a string in "15:04:05" format.
+// ToTimeString outputs a string in "15:04:05" layout.
 // 输出 "15:04:05" 格式字符串
 func (c Carbon) ToTimeString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -249,10 +249,10 @@ func (c Carbon) ToTimeString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(TimeFormat)
+	return c.Carbon2Time().Format(TimeLayout)
 }
 
-// ToShortTimeString outputs a string in "150405" format.
+// ToShortTimeString outputs a string in "150405" layout.
 // 输出 "150405" 格式字符串
 func (c Carbon) ToShortTimeString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -261,16 +261,16 @@ func (c Carbon) ToShortTimeString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ShortTimeFormat)
+	return c.Carbon2Time().Format(ShortTimeLayout)
 }
 
-// ToAtomString outputs a string in "2006-01-02T15:04:05Z07:00" format.
+// ToAtomString outputs a string in "2006-01-02T15:04:05Z07:00" layout.
 // 输出 "2006-01-02T15:04:05Z07:00" 格式字符串
 func (c Carbon) ToAtomString(timezone ...string) string {
 	return c.ToRfc3339String(timezone...)
 }
 
-// ToANSICString outputs a string in "Mon Jan _2 15:04:05 2006" format.
+// ToANSICString outputs a string in "Mon Jan _2 15:04:05 2006" layout.
 // 输出 "Mon Jan _2 15:04:05 2006" 格式字符串
 func (c Carbon) ToANSICString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -279,10 +279,10 @@ func (c Carbon) ToANSICString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ANSICFormat)
+	return c.Carbon2Time().Format(ANSICLayout)
 }
 
-// ToCookieString outputs a string in "Monday, 02-Jan-2006 15:04:05 MST" format.
+// ToCookieString outputs a string in "Monday, 02-Jan-2006 15:04:05 MST" layout.
 // 输出 "Monday, 02-Jan-2006 15:04:05 MST" 格式字符串
 func (c Carbon) ToCookieString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -291,7 +291,7 @@ func (c Carbon) ToCookieString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(CookieFormat)
+	return c.Carbon2Time().Format(CookieLayout)
 }
 
 // ToRssString outputs a string in "Mon, 02 Jan 2006 15:04:05 -0700" format.
@@ -303,16 +303,16 @@ func (c Carbon) ToRssString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RssFormat)
+	return c.Carbon2Time().Format(RssLayout)
 }
 
-// ToW3cString outputs a string in "2006-01-02T15:04:05Z07:00" format.
+// ToW3cString outputs a string in "2006-01-02T15:04:05Z07:00" layout.
 // 输出 "2006-01-02T15:04:05Z07:00" 格式字符串
 func (c Carbon) ToW3cString(timezone ...string) string {
 	return c.ToRfc3339String(timezone...)
 }
 
-// ToUnixDateString outputs a string in "Mon Jan _2 15:04:05 MST 2006" format.
+// ToUnixDateString outputs a string in "Mon Jan _2 15:04:05 MST 2006" layout.
 // 输出 "Mon Jan _2 15:04:05 MST 2006" 格式字符串
 func (c Carbon) ToUnixDateString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -321,10 +321,10 @@ func (c Carbon) ToUnixDateString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(UnixDateFormat)
+	return c.Carbon2Time().Format(UnixDateLayout)
 }
 
-// ToRubyDateString outputs a string in "Mon Jan 02 15:04:05 -0700 2006" format.
+// ToRubyDateString outputs a string in "Mon Jan 02 15:04:05 -0700 2006" layout.
 // 输出 "Mon Jan 02 15:04:05 -0700 2006" 格式字符串
 func (c Carbon) ToRubyDateString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -333,10 +333,10 @@ func (c Carbon) ToRubyDateString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RubyDateFormat)
+	return c.Carbon2Time().Format(RubyDateLayout)
 }
 
-// ToKitchenString outputs a string in "3:04PM" format.
+// ToKitchenString outputs a string in "3:04PM" layout.
 // 输出 "3:04PM" 格式字符串
 func (c Carbon) ToKitchenString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -345,10 +345,10 @@ func (c Carbon) ToKitchenString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(KitchenFormat)
+	return c.Carbon2Time().Format(KitchenLayout)
 }
 
-// ToIso8601String outputs a string in "2006-01-02T15:04:05-07:00" format.
+// ToIso8601String outputs a string in "2006-01-02T15:04:05-07:00" layout.
 // 输出 "2006-01-02T15:04:05-07:00" 格式字符串
 func (c Carbon) ToIso8601String(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -357,10 +357,10 @@ func (c Carbon) ToIso8601String(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ISO8601Format)
+	return c.Carbon2Time().Format(ISO8601Layout)
 }
 
-// ToIso8601MilliString outputs a string in "2006-01-02T15:04:05.999-07:00" format.
+// ToIso8601MilliString outputs a string in "2006-01-02T15:04:05.999-07:00" layout.
 // 输出 "2006-01-02T15:04:05.999-07:00" 格式字符串
 func (c Carbon) ToIso8601MilliString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -369,10 +369,10 @@ func (c Carbon) ToIso8601MilliString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ISO8601MilliFormat)
+	return c.Carbon2Time().Format(ISO8601MilliLayout)
 }
 
-// ToIso8601MicroString outputs a string in "2006-01-02T15:04:05.999999-07:00" format.
+// ToIso8601MicroString outputs a string in "2006-01-02T15:04:05.999999-07:00" layout.
 // 输出 "2006-01-02T15:04:05.999999-07:00" 格式字符串
 func (c Carbon) ToIso8601MicroString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -381,10 +381,10 @@ func (c Carbon) ToIso8601MicroString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ISO8601MicroFormat)
+	return c.Carbon2Time().Format(ISO8601MicroLayout)
 }
 
-// ToIso8601NanoString outputs a string in "2006-01-02T15:04:05.999999999-07:00" format.
+// ToIso8601NanoString outputs a string in "2006-01-02T15:04:05.999999999-07:00" layout.
 // 输出 "2006-01-02T15:04:05.999999999-07:00" 格式字符串
 func (c Carbon) ToIso8601NanoString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -393,10 +393,10 @@ func (c Carbon) ToIso8601NanoString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(ISO8601NanoFormat)
+	return c.Carbon2Time().Format(ISO8601NanoLayout)
 }
 
-// ToRfc822String outputs a string in "02 Jan 06 15:04 MST" format.
+// ToRfc822String outputs a string in "02 Jan 06 15:04 MST" layout.
 // 输出 "02 Jan 06 15:04 MST" 格式字符串
 func (c Carbon) ToRfc822String(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -405,10 +405,10 @@ func (c Carbon) ToRfc822String(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC822Format)
+	return c.Carbon2Time().Format(RFC822Layout)
 }
 
-// ToRfc822zString outputs a string in "02 Jan 06 15:04 -0700" format.
+// ToRfc822zString outputs a string in "02 Jan 06 15:04 -0700" layout.
 // 输出 "02 Jan 06 15:04 -0700" 格式字符串
 func (c Carbon) ToRfc822zString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -417,10 +417,10 @@ func (c Carbon) ToRfc822zString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC822ZFormat)
+	return c.Carbon2Time().Format(RFC822ZLayout)
 }
 
-// ToRfc850String outputs a string in "Monday, 02-Jan-06 15:04:05 MST" format.
+// ToRfc850String outputs a string in "Monday, 02-Jan-06 15:04:05 MST" layout.
 // 输出 "Monday, 02-Jan-06 15:04:05 MST" 格式字符串
 func (c Carbon) ToRfc850String(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -429,10 +429,10 @@ func (c Carbon) ToRfc850String(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC850Format)
+	return c.Carbon2Time().Format(RFC850Layout)
 }
 
-// ToRfc1036String outputs a string in "Mon, 02 Jan 06 15:04:05 -0700" format.
+// ToRfc1036String outputs a string in "Mon, 02 Jan 06 15:04:05 -0700" layout.
 // 输出 "Mon, 02 Jan 06 15:04:05 -0700" 格式字符串
 func (c Carbon) ToRfc1036String(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -441,10 +441,10 @@ func (c Carbon) ToRfc1036String(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC1036Format)
+	return c.Carbon2Time().Format(RFC1036Layout)
 }
 
-// ToRfc1123String outputs a string in "Mon, 02 Jan 2006 15:04:05 MST" format.
+// ToRfc1123String outputs a string in "Mon, 02 Jan 2006 15:04:05 MST" layout.
 // 输出 "Mon, 02 Jan 2006 15:04:05 MST" 格式字符串
 func (c Carbon) ToRfc1123String(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -453,10 +453,10 @@ func (c Carbon) ToRfc1123String(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC1123Format)
+	return c.Carbon2Time().Format(RFC1123Layout)
 }
 
-// ToRfc1123zString outputs a string in "Mon, 02 Jan 2006 15:04:05 -0700" format.
+// ToRfc1123zString outputs a string in "Mon, 02 Jan 2006 15:04:05 -0700" layout.
 // 输出 "Mon, 02 Jan 2006 15:04:05 -0700" 格式字符串
 func (c Carbon) ToRfc1123zString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -465,10 +465,10 @@ func (c Carbon) ToRfc1123zString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC1123ZFormat)
+	return c.Carbon2Time().Format(RFC1123ZLayout)
 }
 
-// ToRfc2822String outputs a string in "Mon, 02 Jan 2006 15:04:05 -0700" format.
+// ToRfc2822String outputs a string in "Mon, 02 Jan 2006 15:04:05 -0700" layout.
 // 输出 "Mon, 02 Jan 2006 15:04:05 -0700" 格式字符串
 func (c Carbon) ToRfc2822String(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -477,10 +477,10 @@ func (c Carbon) ToRfc2822String(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC2822Format)
+	return c.Carbon2Time().Format(RFC2822Layout)
 }
 
-// ToRfc3339String outputs a string in "2006-01-02T15:04:05Z07:00" format.
+// ToRfc3339String outputs a string in "2006-01-02T15:04:05Z07:00" layout.
 // 输出 "2006-01-02T15:04:05Z07:00" 格式字符串
 func (c Carbon) ToRfc3339String(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -489,10 +489,10 @@ func (c Carbon) ToRfc3339String(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC3339Format)
+	return c.Carbon2Time().Format(RFC3339Layout)
 }
 
-// ToRfc3339MilliString outputs a string in "2006-01-02T15:04:05.999Z07:00" format.
+// ToRfc3339MilliString outputs a string in "2006-01-02T15:04:05.999Z07:00" layout.
 // 输出 "2006-01-02T15:04:05.999Z07:00" 格式字符串
 func (c Carbon) ToRfc3339MilliString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -501,10 +501,10 @@ func (c Carbon) ToRfc3339MilliString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC3339MilliFormat)
+	return c.Carbon2Time().Format(RFC3339MilliLayout)
 }
 
-// ToRfc3339MicroString outputs a string in "2006-01-02T15:04:05.999999Z07:00" format.
+// ToRfc3339MicroString outputs a string in "2006-01-02T15:04:05.999999Z07:00" layout.
 // 输出 "2006-01-02T15:04:05.999999Z07:00" 格式字符串
 func (c Carbon) ToRfc3339MicroString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -513,10 +513,10 @@ func (c Carbon) ToRfc3339MicroString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC3339MicroFormat)
+	return c.Carbon2Time().Format(RFC3339MicroLayout)
 }
 
-// ToRfc3339NanoString outputs a string in "2006-01-02T15:04:05.999999999Z07:00" format.
+// ToRfc3339NanoString outputs a string in "2006-01-02T15:04:05.999999999Z07:00" layout.
 // 输出 "2006-01-02T15:04:05.999999999Z07:00" 格式字符串
 func (c Carbon) ToRfc3339NanoString(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -525,10 +525,10 @@ func (c Carbon) ToRfc3339NanoString(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC3339NanoFormat)
+	return c.Carbon2Time().Format(RFC3339NanoLayout)
 }
 
-// ToRfc7231String outputs a string in "Mon, 02 Jan 2006 15:04:05 GMT" format.
+// ToRfc7231String outputs a string in "Mon, 02 Jan 2006 15:04:05 GMT" layout.
 // 输出 "Mon, 02 Jan 2006 15:04:05 GMT" 格式字符串
 func (c Carbon) ToRfc7231String(timezone ...string) string {
 	if len(timezone) > 0 {
@@ -537,7 +537,7 @@ func (c Carbon) ToRfc7231String(timezone ...string) string {
 	if c.IsInvalid() {
 		return ""
 	}
-	return c.Carbon2Time().Format(RFC7231Format)
+	return c.Carbon2Time().Format(RFC7231Layout)
 }
 
 // ToLayoutString outputs a string by layout.
diff --git a/parser.go b/parser.go
index 00d40cf0..7ed1d99d 100755
--- a/parser.go
+++ b/parser.go
@@ -9,32 +9,32 @@ import (
 // Parse parses a standard string as a Carbon instance.
 // 将标准格式时间字符串解析成 Carbon 实例
 func (c Carbon) Parse(value string, timezone ...string) Carbon {
-	layout := DateTimeFormat
+	layout := DateTimeLayout
 	if _, err := strconv.ParseInt(value, 10, 64); err == nil {
 		switch {
 		case len(value) == 8:
-			layout = ShortDateFormat
+			layout = ShortDateLayout
 		case len(value) == 14:
-			layout = ShortDateTimeFormat
+			layout = ShortDateTimeLayout
 		}
 	} else {
 		switch {
 		case len(value) == 10 && strings.Count(value, "-") == 2:
-			layout = DateFormat
+			layout = DateLayout
 		case len(value) == 18 && strings.Index(value, ".") == 14:
-			layout = ShortDateTimeMilliFormat
+			layout = ShortDateTimeMilliLayout
 		case len(value) == 21 && strings.Index(value, ".") == 14:
-			layout = ShortDateTimeMicroFormat
+			layout = ShortDateTimeMicroLayout
 		case len(value) == 24 && strings.Index(value, ".") == 14:
-			layout = ShortDateTimeNanoFormat
+			layout = ShortDateTimeNanoLayout
 		case len(value) == 25 && strings.Index(value, "T") == 10:
-			layout = RFC3339Format
+			layout = RFC3339Layout
 		case len(value) == 29 && strings.Index(value, "T") == 10 && strings.Index(value, ".") == 19:
-			layout = RFC3339MilliFormat
+			layout = RFC3339MilliLayout
 		case len(value) == 32 && strings.Index(value, "T") == 10 && strings.Index(value, ".") == 19:
-			layout = RFC3339MicroFormat
+			layout = RFC3339MicroLayout
 		case len(value) == 35 && strings.Index(value, "T") == 10 && strings.Index(value, ".") == 19:
-			layout = RFC3339NanoFormat
+			layout = RFC3339NanoLayout
 		}
 	}
 	carbon := c.ParseByLayout(value, layout, timezone...)
diff --git a/parser_test.go b/parser_test.go
index fe82b26c..0e83d2df 100755
--- a/parser_test.go
+++ b/parser_test.go
@@ -112,7 +112,7 @@ func TestCarbon_ParseByLayout(t *testing.T) {
 }
 
 func TestError_Parse(t *testing.T) {
-	date, layout, format, timezone := "2020-08-50", "2006-01-02", DateFormat, "xxx"
+	date, layout, format, timezone := "2020-08-50", "2006-01-02", DateLayout, "xxx"
 	assert.NotNil(t, Parse(date).Error, "It should catch an exception in Parse()")
 	assert.NotNil(t, ParseByLayout(date, layout, timezone).Error, "It should catch an exception in ParseByLayout()")
 	assert.NotNil(t, ParseByFormat(date, format, timezone).Error, "It should catch an exception in ParseByFormat()")