os.date函式定義

• 原型：os.date ([format [, time]])
• 解釋：返回一個按format格式化日期、時間的字串或表。

lua原始碼中os.date的註釋如下：

---
--- Returns a string or a table containing date and time, formatted according
--- to the given string `format`.
---
--- If the `time` argument is present, this is the time to be formatted (see
--- the `os.time` function for a description of this value). Otherwise,
--- `date` formats the current time.
---
--- If `format` starts with '`!`', then the date is formatted in Coordinated
--- Universal Time. After this optional character, if `format` is the string
--- "`*t`", then `date` returns a table with the following fields:
---
--- **`year`** (four digits)
--- **`month`** (1–12)
--- **`day`** (1-31)
--- **`hour`** (0-23)
--- **`min`** (0-59)
--- **`sec`** (0-61), due to leap seconds
--- **`wday`** (weekday, 1–7, Sunday is 1)
--- **`yday`** (day of the year, 1–366)
--- **`isdst`** (daylight saving flag, a boolean). This last field may be absent
--- if the information is not available.
---
--- If `format` is not "`*t`", then `date` returns the date as a string,
--- formatted according to the same rules as the ISO C function `strftime`.
---
--- When called without arguments, `date` returns a reasonable date and time
--- representation that depends on the host system and on the current locale.
--- (More specifically, `os.date()` is equivalent to `os.date("%c")`.)
---
--- On non-POSIX systems, this function may be not thread safe because of its
--- reliance on C function `gmtime` and C function `localtime`.
 
[email protected] fun():string|table
[email protected] format string
[email protected] time number
[email protected] string|table
function os.date(format, time) end

os.date格式符對照表

os.date ([format [, time]])

由原型可以看出可以省略第二個引數也可以省略兩個引數，

只省略第二個引數函式會使用當前時間作為第二個引數，

如果兩個引數都省略則按當前系統的設定返回格式化的字串，做以下等價替換 os.date() <=> os.date("%c")。

如果format以 “!” 開頭，則按格林尼治時間進行格式化。

如果format是一個 “t” ，將返一個帶year(4位)，month(1-12)， day (1--31)， hour (0-23)， min (0-59)，sec (0-61)，wday (星期幾， 星期天為1)， yday (年內天數)和isdst (是否為日光節約時間true/false)的帶鍵名的表;

如果format不是 “t” ，os.date會將日期格式化為一個字串，具體如下：

使用示例

我的lua版本：lua5.3

print ("os.date(\"*t\") 示例:\n")
local timetable = os.date("*t", os.time());
for i, v in pairs(timetable) do
    print(i, v);
end

print ("\n \"!\" 開頭:\n")
local utimetable = os.date("!*t", os.time());
for i, v in pairs(utimetable) do
    print(i, v);
end

print ("\n其它用法:\n")
print(os.date("今天是 %c, 星期 %A"))

輸出結果：

今天東八區中國廣州的日期為：2018-11-1 21:13 星期四

os.date("*t") 示例:
wday    5
year    2018
day     1
sec     51
hour    21
isdst   false
month   11
yday    305
min     13

os.date("!*t") 示例:
wday    5
year    2018
day     1
sec     38
hour    13  --- 差8小時
isdst   false
month   11
yday    305
min     14

今天是 11/01/18 21:15:36, 星期 Thursday

• 注意format "!" 的用法，因為我們的時間（北京）處於東8區，所以兩次的結果會差8個小時(13+8=21)，從結果中可以看出。
• 注意使用format "*t"返回的table中wday如果是1表示星期天，而使用通用格式時%w用0表示星期天。

參考：https://www.jianshu.com/p/76ac11863591