英文:
Go - Unix timestamp for first day of the week from ISO year week
问题
获取2010年第五周星期一00:00:00的时间戳有什么好的方法？实际上，我正在寻找与time包中的ISOweek函数相反的函数。我似乎找不到实现这一目标的方法。Parse()函数无法读取周数，而且仅仅计算自年/月的第一天以来有多少个"7天"并不能满足我的需求。
非常感谢！
Bill
英文:
What's a good way of getting the timestamp for, say, the Monday 00:00:00 for the fifth week of 2010? Essentially I'm looking for the inverse function to ISOweek in the time package. I can't seem to find a way to achieve that. Parse() doesn't read week, and simply counting how many "7 days" there have been since the first day of the year/month doesn't really get me what I need.
Thanks a lot in advance!
Bill
答案1
得分: 11
我不明白为什么仅仅计算自年/月的第一天以来有多少个“7天”并不能满足我的需求。
这是我的尝试：
func firstDayOfISOWeek(year int, week int, timezone *time.Location) time.Time {
date := time.Date(year, 0, 0, 0, 0, 0, 0, timezone)
isoYear, isoWeek := date.ISOWeek()
for date.Weekday() != time.Monday { // 迭代回到星期一
date = date.AddDate(0, 0, -1)
isoYear, isoWeek = date.ISOWeek()
}
for isoYear < year { // 迭代前进到第一周的第一天
date = date.AddDate(0, 0, 1)
isoYear, isoWeek = date.ISOWeek()
}
for isoWeek < week { // 迭代前进到给定周的第一天
date = date.AddDate(0, 0, 1)
isoYear, isoWeek = date.ISOWeek()
}
return date
}
这是一个带有健全性检查的可工作示例：http://play.golang.org/p/UVFNFcpaoI
这段代码很容易理解，没有年/月/日的计算，只是简单的迭代。运行时复杂度为O(n)，但考虑到n始终小于400，实际上并不是问题。
如果golang的date.AddDate实现正确，它不应该在夏令时、闰年和其他棘手的日期问题上出现问题。
附：有趣的事实 
2008年第1周的第一天是2007-12-31。这是正确的，你可以在日历中查看。
英文:
I don't see why
> simply counting how many "7 days" there have been since the first day of the year/month doesn't really get me what I need
Here is my attempt:
func firstDayOfISOWeek(year int, week int, timezone *time.Location) time.Time {
date := time.Date(year, 0, 0, 0, 0, 0, 0, timezone)
isoYear, isoWeek := date.ISOWeek()
for date.Weekday() != time.Monday { // iterate back to Monday
date = date.AddDate(0, 0, -1)
isoYear, isoWeek = date.ISOWeek()
}
for isoYear < year { // iterate forward to the first day of the first week
date = date.AddDate(0, 0, 1)
isoYear, isoWeek = date.ISOWeek()
}
for isoWeek < week { // iterate forward to the first day of the given week
date = date.AddDate(0, 0, 1)
isoYear, isoWeek = date.ISOWeek()
}
return date
}
Here is working example with sanity check: http://play.golang.org/p/UVFNFcpaoI
The code is easy to understand, there is no year/month/day arithmetic, just simple iteration. The runtime complexity is O(n), but given that n is always less than 400 - it's actually not a problem at all.
It should not have problems with daylight saving, leap years and other tricky date problems if golang date.AddDate is implemented correctly.
P.S. Funny fact First day of week 1 of year 2008 is 2007-12-31. And this is correct, you can check in the calendar.
答案2
得分: 4
我为了这个目的实现了另一个简单的Go包：
https://github.com/snabb/isoweek
示例用法：
st := isoweek.StartTime(1985, 1, time.UTC)
fmt.Println(st)
// 输出：
// 1984-12-31 00:00:00 +0000 UTC
我不喜欢被接受的答案中的方法，因为它来回迭代，这是荒谬的。
我也不喜欢另一个答案中的goweek包，因为它似乎过于复杂，API也很奇怪（为什么要可变参数等）。
英文:
I implemented yet another simple Go package for exactly this purpose:
https://github.com/snabb/isoweek
Example usage:
st := isoweek.StartTime(1985, 1, time.UTC)
fmt.Println(st)
// Output:
// 1984-12-31 00:00:00 +0000 UTC
I did not like the method in the accepted answer because it iterates backwards and forwards which is ridiculous.
I also did not like goweek package in another answer as it seems overly complicated and the API is very strange (why variadic arguments? etc).
答案3
得分: 1
func GetStartDayOfWeek(tm time.Time) time.Time { //获取周一的00:00:00
weekday := time.Duration(tm.Weekday())
if weekday == 0 {
weekday = 7
}
year, month, day := t.Date()
currentZeroDay := time.Date(year, month, day, 0, 0, 0, 0, time.Local)
return currentZeroDay.Add(-1 * (weekday - 1) * 24 * time.Hour)
}
英文:
func GetStartDayOfWeek(tm time.Time) time.Time { //get monday 00:00:00
weekday := time.Duration(tm.Weekday())
if weekday == 0 {
weekday = 7
}
year, month, day := t.Date()
currentZeroDay:= time.Date(year, month, day, 0, 0, 0, 0, time.Local)
return currentZeroDay.Add(-1 * (weekday - 1) * 24 * time.Hour)
}
答案4
得分: 0
无耻地自我推广一下，我刚刚发布了一个用于在Go中处理周的库：https://github.com/grsmv/goweek
英文:
Shameless self-promotion, but I just released lib for working with weeks in Go: https://github.com/grsmv/goweek
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