阅读golang time文档

Golang/Golang Document.md

@@ -63,6 +63,13 @@
 		- [format time](#format-time)
 			- [使用预定义的time Format](#使用预定义的time-format)
 		- [字符串转日期/时间](#字符串转日期时间)
+		- [timeZone](#timezone)
+			- [ParseInLocation](#parseinlocation)
+			- [获取UTC时间](#获取utc时间)
+			- [获取Local时间](#获取local时间)
+		- [compare time](#compare-time)
+		- [Sub](#sub)
+		- [time.Duration](#timeduration)
 	- [syntax](#syntax)
 		- [iota](#iota)
 
@@ -1296,11 +1303,177 @@ func main() {
 time.Parse除了返回time.Time类型的值之外，还返回一个error对象。
 
 
+### timeZone
+当formatLayout中不包含时区且被转换的日期字符串中也不包含时区时，`time.Parse`方法在转换日期字符串时会使用默认的时区。
 
+> #### 默认时区
+> 默认时区为"+0000`时区，也被称为UTC时区。
 
+示例如下：
+```go
+t, err := time.Parse("2006-01-02 15:04:05", "2024-10-25 12:13:14")
+if err != nil {
+	panic(any(err))
+}
+fmt.Println(t)
+```
+上述示例输出内容为
+```
+2024-10-25 12:13:14 +0000 UTC
+```
+其在未指定时区时默认使用UTC时区。
 
+#### ParseInLocation
+如果在转换未包含时区信息的字符串中，使用指定时区，可以调用`ParseInLocation`方法，示例如下
+```go
+	var (
+		t time.Time
+		cst *time.Location
+		err error
+	)
+	cst, err = time.LoadLocation("Asia/Shanghai")
+	if err != nil {
+		panic(any(err))
+	}
+	t, err = time.ParseInLocation("2006-01-02 15:04:05", "2024-10-25 12:13:14", cst)
+	if err != nil {
+		panic(any(err))
+	}
+	fmt.Println(t)
+```
 
+#### 获取UTC时间
+通过调用`time.UTC`方法，可以将当前时间转换为UTC时间，示例如下：
+```go
+	now := time.Now()
+	fmt.Println("current time is ", now)
+	fmt.Println("current utc time is ", now.UTC())
+```
+上述示例输出为
+```
+current time is  2025-01-17 13:46:20.6897373 +0800 CST m=+0.000000001
+current utc time is  2025-01-17 05:46:20.6897373 +0000 UTC
+```
+可见将cst时区转化为utc时区时，小时部分`-8`
 
+#### 获取Local时间
+相对的，将UTC或其他时区的时间转化为本地时区的时间时，可以调用`Local`方法
+```go
+	var (
+		t time.Time
+		err error
+	)
+	t, err = time.ParseInLocation("2006-01-02 15:04:05", "2010-12-18 19:03:32", time.UTC)
+	if err != nil {
+		panic(any(err))
+	}
+	fmt.Println("utc time is ", t)
+	fmt.Println("local time is ", t.Local())
+```
+其输出结果如下：
+```
+utc time is  2010-12-18 19:03:32 +0000 UTC
+local time is  2010-12-19 03:03:32 +0800 CST
+```
+
+### compare time
+对于日期的比较，golang提供了`Before`, `After`, `Equal`方法，
+
+其使用示例如下：
+```go
+	var (
+		t1 time.Time
+		t2 time.Time
+		err error
+	)
+	t1, err = time.ParseInLocation("2006-01-02 15:04:05", "2010-12-18 19:03:32", time.UTC)
+	if err != nil {
+		panic(any(err))
+	}
+	t2, err = time.ParseInLocation("2006-01-02 15:04:05", "2010-12-19 03:03:33", time.Local)
+	fmt.Println("t1 utc time is ", t1.UTC())
+	fmt.Println("t2 utc time is ", t2.UTC())
+	fmt.Println(t1.Equal(t2))
+	fmt.Println(t1.Before(t2))
+	fmt.Println(t1.After(t2))
+```
+其输出为
+```
+t1 utc time is  2010-12-18 19:03:32 +0000 UTC
+t2 utc time is  2010-12-18 19:03:33 +0000 UTC
+false
+true
+false
+```
+
+### Sub
+除了通过上述方法进行比较外，针对两个`time.Time`类型还支持`Sub`方法，该方法会返回`time.Duration`类型的值。
+
+`Sub`方法的使用示例如下：
+```go
+	var (
+		t1 time.Time
+		t2 time.Time
+		err error
+	)
+	t1, err = time.ParseInLocation("2006-01-02 15:04:05", "2010-12-18 19:03:32", time.UTC)
+	if err != nil {
+		panic(any(err))
+	}
+	t2, err = time.ParseInLocation("2006-01-02 15:04:05", "2010-12-19 03:03:33", time.Local)
+	fmt.Println("t1 utc time is ", t1.UTC())
+	fmt.Println("t2 utc time is ", t2.UTC())
+	fmt.Println("t2 - t1 = ", t2.Sub(t1))
+```
+上述代码输出为
+```
+t1 utc time is  2010-12-18 19:03:32 +0000 UTC
+t2 utc time is  2010-12-18 19:03:33 +0000 UTC
+t2 - t1 =  1s
+```
+
+### time.Duration
+在golang中，`time.Duration`类型定义如下：
+```go
+type Duration int64
+```
+在time包中，还定义了诸多`time.Duration`类型的常量，示例如下：
+```go
+const (
+	Nanosecond  Duration = 1
+	Microsecond          = 1000 * Nanosecond
+	Millisecond          = 1000 * Microsecond
+	Second               = 1000 * Millisecond
+	Minute               = 60 * Second
+	Hour                 = 60 * Minute
+)
+```
+如上所示，`time.Duration`类型的底层类型为int64，并且最小单位为`nanos`。
+
+故而，使用`10 * time.Minute`, `3 * time.Hour`等表达式，可以定义自己的time.Duration值。
+
+对于`time.Time`类型，支持通过`Add`方法来对时间进行加减，`Add`方法接收一个`time.Duration`类型的参数，返回值为`time.Time`类型
+```go
+	var (
+		t1 time.Time
+		err error
+	)
+	t1, err = time.ParseInLocation("2006-01-02 15:04:05", "2010-12-18 19:03:32", time.UTC)
+	if err != nil {
+		panic(any(err))
+	}
+	t2 := t1.Add(time.Hour * 24)
+	t3 := t1.Add(time.Hour * -24)
+	fmt.Println(t1)
+	fmt.Println(t2)
+	fmt.Println(t3)
+```
+上述示例的返回结果为
+```
+2010-12-18 19:03:32 +0000 UTC
+2010-12-19 19:03:32 +0000 UTC
+2010-12-17 19:03:32 +0000 UTC
+```
 
 
 ## syntax