Initialize

Guardfile

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+guard 'gotest' do
+  watch(%r{\.go$})
+end

README.md

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+= Now
+
+Now is a time toolkit for golang
+
+== Why the project named Now?
+
+```go
+now.BeginningOfDay()
+```
+`now` is quite readable, aha?
+
+== But `now` is so common I can't find it with my favorite search engine
+
+* Star it in github [https://github.com/jinzhu/now](https://github.com/jinzhu/now)
+* Search it with [http://godoc.org](http://godoc.org)
+
+== Usage
+
+```go
+time.Now() // 2013-11-18 17:51:49.123456789 Mon
+
+now.BeginningOfMinute() // 2013-11-18 17:51:00 Mon
+now.BeginningOfHour()   // 2013-11-18 17:00:00 Mon
+now.BeginningOfDay()    // 2013-11-18 00:00:00 Mon
+now.BeginningOfWeek()   // 2013-11-17 00:00:00 Sun
+
+now.FirstDayMonday = true // Set Monday as first day
+now.BeginningOfWeek()     // 2013-11-18 00:00:00 Mon
+now.BeginningOfMonth()    // 2013-11-01 00:00:00 Fri
+now.BeginningOfYear()     // 2013-01-01 00:00:00 Tue
+
+now.EndOfMinute()         // 2013-11-18 17:51:59.999999999 Mon
+now.EndOfHour()           // 2013-11-18 17:59:59.999999999 Mon
+now.EndOfDay()            // 2013-11-18 23:59:59.999999999 Mon
+now.EndOfWeek()           // 2013-11-23 23:59:59.999999999 Sat
+
+now.FirstDayMonday = true // Set Monday as first day
+now.EndOfWeek()           // 2013-11-24 23:59:59.999999999 Sun
+now.EndOfMonth()          // 2013-11-30 23:59:59.999999999 Sat
+now.EndOfYear()           // 2013-12-31 23:59:59.999999999 Tue
+
+// Use another time
+t := time.Date(2013, 02, 18, 17, 51, 49, 123456789, time.Now().Location())
+now.New(t).EndOfMonth()   // 2013-02-28 23:59:59.999999999 Thu
+```

main.go

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+// Package now is a time toolkit for golang.
+package now
+
+import "time"
+
+var FirstDayMonday bool
+
+func init() {
+	FirstDayMonday = false
+}
+
+type Now struct {
+	time   time.Time
+	format string
+}
+
+func New(t time.Time) *Now {
+	return &Now{time: t}
+}
+
+func BeginningOfMinute() time.Time {
+	return New(time.Now()).BeginningOfMinute()
+}
+
+func BeginningOfHour() time.Time {
+	return New(time.Now()).BeginningOfHour()
+}
+
+func BeginningOfDay() time.Time {
+	return New(time.Now()).BeginningOfDay()
+}
+
+func BeginningOfWeek() time.Time {
+	return New(time.Now()).BeginningOfWeek()
+}
+
+func BeginningOfMonth() time.Time {
+	return New(time.Now()).BeginningOfMonth()
+}
+
+func BeginningOfYear() time.Time {
+	return New(time.Now()).BeginningOfYear()
+}
+
+func EndOfMinute() time.Time {
+	return New(time.Now()).EndOfMinute()
+}
+
+func EndOfHour() time.Time {
+	return New(time.Now()).EndOfHour()
+}
+
+func EndOfDay() time.Time {
+	return New(time.Now()).EndOfDay()
+}
+
+func EndOfWeek() time.Time {
+	return New(time.Now()).EndOfWeek()
+}
+
+func EndOfMonth() time.Time {
+	return New(time.Now()).EndOfMonth()
+}
+
+func EndOfYear() time.Time {
+	return New(time.Now()).EndOfYear()
+}

now.go

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+package now
+
+import "time"
+
+func (now *Now) BeginningOfMinute() time.Time {
+	return now.time.Truncate(time.Minute)
+}
+
+func (now *Now) BeginningOfHour() time.Time {
+	return now.time.Truncate(time.Hour)
+}
+
+func (now *Now) BeginningOfDay() time.Time {
+	d := time.Duration(-now.time.Hour()) * time.Hour
+	return now.time.Truncate(time.Hour).Add(d)
+}
+
+func (now *Now) BeginningOfWeek() time.Time {
+	t := now.BeginningOfDay()
+	weekday := int(t.Weekday())
+	if FirstDayMonday {
+		if weekday == 0 {
+			weekday = 7
+		}
+		weekday = weekday - 1
+	}
+
+	d := time.Duration(-weekday) * 24 * time.Hour
+	return t.Truncate(time.Hour).Add(d)
+}
+
+func (now *Now) BeginningOfMonth() time.Time {
+	t := now.BeginningOfDay()
+	d := time.Duration(-int(t.Day())+1) * 24 * time.Hour
+	return t.Truncate(time.Hour).Add(d)
+}
+
+func (now *Now) BeginningOfYear() time.Time {
+	t := now.BeginningOfDay()
+	d := time.Duration(-int(t.YearDay())+1) * 24 * time.Hour
+	return t.Truncate(time.Hour).Add(d)
+}
+
+func (now *Now) EndOfMinute() time.Time {
+	return now.BeginningOfMinute().Add(time.Minute - time.Nanosecond)
+}
+
+func (now *Now) EndOfHour() time.Time {
+	return now.BeginningOfHour().Add(time.Hour - time.Nanosecond)
+}
+
+func (now *Now) EndOfDay() time.Time {
+	return now.BeginningOfDay().Add(24*time.Hour - time.Nanosecond)
+}
+
+func (now *Now) EndOfWeek() time.Time {
+	return now.BeginningOfWeek().AddDate(0, 0, 7).Add(-time.Nanosecond)
+}
+
+func (now *Now) EndOfMonth() time.Time {
+	return now.BeginningOfMonth().AddDate(0, 1, 0).Add(-time.Nanosecond)
+}
+
+func (now *Now) EndOfYear() time.Time {
+	return now.BeginningOfYear().AddDate(1, 0, 0).Add(-time.Nanosecond)
+}

now_test.go

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+package now
+
+import (
+	"testing"
+	"time"
+)
+
+var format string
+
+func init() {
+	format = "2006-01-02 15:04:05.999999999"
+}
+
+func TestBeginningOf(t *testing.T) {
+	n := time.Date(2013, 11, 18, 17, 51, 49, 123456789, time.Now().Location())
+
+	if New(n).BeginningOfMinute().Format(format) != "2013-11-18 17:51:00" {
+		t.Errorf("BeginningOfMinute")
+	}
+
+	if New(n).BeginningOfHour().Format(format) != "2013-11-18 17:00:00" {
+		t.Errorf("BeginningOfHour")
+	}
+
+	if New(n).BeginningOfDay().Format(format) != "2013-11-18 00:00:00" {
+		t.Errorf("BeginningOfDay")
+	}
+
+	FirstDayMonday = true
+	if New(n).BeginningOfWeek().Format(format) != "2013-11-18 00:00:00" {
+		t.Errorf("BeginningOfWeek, FirstDayMonday")
+	}
+
+	FirstDayMonday = false
+	if New(n).BeginningOfWeek().Format(format) != "2013-11-17 00:00:00" {
+		t.Errorf("BeginningOfWeek")
+	}
+
+	if New(n).BeginningOfMonth().Format(format) != "2013-11-01 00:00:00" {
+		t.Errorf("BeginningOfMonth")
+	}
+
+	if New(n).BeginningOfYear().Format(format) != "2013-01-01 00:00:00" {
+		t.Errorf("BeginningOfYear")
+	}
+}
+
+func TestEndOf(t *testing.T) {
+	n := time.Date(2013, 11, 18, 17, 51, 49, 123456789, time.Now().Location())
+
+	if New(n).EndOfMinute().Format(format) != "2013-11-18 17:51:59.999999999" {
+		t.Errorf("EndOfMinute")
+	}
+
+	if New(n).EndOfHour().Format(format) != "2013-11-18 17:59:59.999999999" {
+		t.Errorf("EndOfHour")
+	}
+
+	if New(n).EndOfDay().Format(format) != "2013-11-18 23:59:59.999999999" {
+		t.Errorf("EndOfDay")
+	}
+
+	FirstDayMonday = true
+	if New(n).EndOfWeek().Format(format) != "2013-11-24 23:59:59.999999999" {
+		t.Errorf("EndOfWeek, FirstDayMonday")
+	}
+
+	FirstDayMonday = false
+	if New(n).EndOfWeek().Format(format) != "2013-11-23 23:59:59.999999999" {
+		t.Errorf("EndOfWeek")
+	}
+
+	if New(n).EndOfMonth().Format(format) != "2013-11-30 23:59:59.999999999" {
+		t.Errorf("EndOfMonth")
+	}
+
+	if New(n).EndOfYear().Format(format) != "2013-12-31 23:59:59.999999999" {
+		t.Errorf("EndOfYear")
+	}
+
+	n1 := time.Date(2013, 02, 18, 17, 51, 49, 123456789, time.Now().Location())
+	if New(n1).EndOfMonth().Format(format) != "2013-02-28 23:59:59.999999999" {
+		t.Errorf("EndOfMonth for 2013/02")
+	}
+
+	n2 := time.Date(1900, 02, 18, 17, 51, 49, 123456789, time.Now().Location())
+	if New(n2).EndOfMonth().Format(format) != "1900-02-28 23:59:59.999999999" {
+		t.Errorf("EndOfMonth")
+	}
+}