在lua中来回UTC日期 [英] Back and forth UTC dates in lua

问题描述

我在将Lua日期转换为时间戳然后从中获取原始日期时遇到问题.它适用于非UTC日期，但不适用于UTC.

I'm having problems converting a lua date to a timestamp and then obtaining back the original date from it. It does work for non UTC dates, but not with UTC.

当前我的示例代码为:

local dt1 = os.date( "*t" );
print( dt1.hour );

local dt2 = os.date( "*t", os.time( dt1 ) );
print( dt2.hour );

print( "-=-=-" );

local dt1 = os.date( "!*t" );
print( dt1.hour );

local dt2 = os.date( "!*t", os.time( dt1 ) );
print( dt2.hour );

local dt2 = os.date( "*t", os.time( dt1 ) );
print( dt2.hour );

哪个输出:

12
12
-=-=-
10
9
11

因此，在第二部分中，使用os.time( os.date( "!*t" ) )获得时间戳后；我不知道如何获取原始日期.我做错了什么事?

So, in the second part, after obtaining the timestamp using os.time( os.date( "!*t" ) ); I don't know how to obtain the original date back. What is it that I'm doing wrong?

推荐答案

在Lua中使用日期表"

让dt成为日期表".
例如，os.date("*t")返回的值是日期表".

Working with "date tables" in Lua

Let dt be a "date table".
For example, a value returned by os.date("*t") is a "date table".

如何规范化日期表"
例如，在当前时间加上1.5小时后
local dt = os.date("*t"); dt.min = dt.min + 90
您需要规范化表格字段.

How to normalize "date table"
For example, after adding 1.5 hours to the current time
local dt = os.date("*t"); dt.min = dt.min + 90
you need to normalize the table fields.

function normalize_date_table(dt)
   return os.date("*t", os.time(dt))
end

此函数将返回与它的参数dt等效的新日期表，无论dt的内容是什么含义:它是否包含本地时间或格林尼治标准时间.

This function returns new date table which is equivalent to its argument dt regardless of the meaning of content of dt: whether it contains local or GMT time.

如何将Unix时间转换为本地日期表"

dt = os.date("*t", ux_time)

---

如何将Unix时间转换为"GMT日期表"

dt = os.date("!*t", ux_time)

---

如何将本地日期表"转换为Unix时间

ux_time = os.time(dt)

---

如何将"GMT日期表"转换为Unix时间

-- for this conversion we need precalculated value "zone_diff"
local tmp_time = os.time()
local d1 = os.date("*t",  tmp_time)
local d2 = os.date("!*t", tmp_time)
d1.isdst = false
local zone_diff = os.difftime(os.time(d1), os.time(d2))
-- zone_diff value may be calculated only once (at the beginning of your program)

-- now we can perform the conversion (dt -> ux_time):
dt.sec = dt.sec + zone_diff
ux_time = os.time(dt)

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