os

This library currently serves the purpose of providing information about the system time under the UTC format. It has been heavily sandboxed from the standard Lua os library and does not allow you to perform any system-altering operations.

int os.time ( table time = UTC time )
Returns how many seconds have passed since the Unix epoch (1 January 1970, 00:00:00), under current UTC time. If provided a table formatted similarly to that returned by `os.date`, it will return the number of seconds since that time instead. print(os.time()) --> 1586982482 (ran at approx. April 15th, 2020 at 1:28 PM PST) print(os.time({ year=2020, month=4, day=15, -- Date components hour=16, min=28, sec=0 -- Time components })) --> 1586968080

int os.difftime ( int t2, int t1 )
Returns the number of seconds from t1 to t2. The difference is computed assuming that t1 and t2 are correctly casted to the time_t format.

dictionary os.date ( string formatString, int time )

Formats the given formatString with date/time information based on the given time, or if not provided, the value returned by os.time. The following specifiers (based on the C function strftime) are supported:

Specifier	Meaning	Example^†
%a	Abbreviated weekday name *	Wed
%A	Full weekday name *	Wednesday
%b	Abbreviated month name *	Sep
%B	Full month name *	September
%c	Date and time *	09/16/98 23:48:10
%d	Day of the month	16
%H	Hour, using 24-hour clock	23
%I	Hour, using 12-hour clock	11
%j	Day of year	259
%m	Month	09
%M	Minute	48
%p	Either "AM" or "PM"	pm
%S	Second	10
%U	Week number (first Sunday as the first day of week one)	37
%w	Weekday	3
%W	Week number (first Monday as the first day of week one)	37
%x	Date *	09/16/98
%X	Time *	23:48:10
%y	Two-digit year	98
%Y	Full year	1998
%z	ISO 8601 offset from UTC in timezone (1 minute = 1, 1 hour = 100)	-0400
%Z	Timezone name or abbreviation *	Eastern Daylight Time
%%	The % character	%

* This value can vary depending on the current locale.
† The example provided is for September 16th, 1998 (a Wednesday) at 11:48:10 PM (23:48:10), ran using locale “en-us” in Eastern Time (ET).

If the provided formatString is exactly "*t" (local time) or "!*t" (UTC time), this function instead returns a dictionary containing the following components, which are normally available in the specifiers above.

Field	Type	Description
year	int	An integer that describes the current year of the Current Era (ex. 2017)
month	int	An integer between 1 and 12 (starting from January) that describes the current month.
wday	int	An integer between 1 and 7 (starting from Sunday) that describes the current week day.
yday	int	An integer between 1 and 366 describing how many days we are into the year. There can be 366 days if it is a leap year.
day	int	An integer between 1 and 31 describing the current day of the month.
hour	int	An integer between 1 and 24 describing the current hour of the day.
min	int	An integer between 0 and 59 describing the current minute of the hour.
sec	int	An integer between 0 and 60 describing the current second of the hour. (60 because the function is described to indicate leap seconds, but in practice it probably doesn't).
isdst	bool	A boolean describing if daylight savings time is currently active.

os.clock ( )

Returns the amount of CPU time used by Lua in seconds. This value has high precision, about 1 microsecond, and is intended for use in benchmarking.

-- Record the initial time:
local startTime = os.clock()
-- Do something you want to measure the performance of:
local a, b = 0, 1
for i = 1, 5000000 do
    a, b = b, a
end
-- Measure amount of time this took:
local deltaTime = os.clock() - startTime
print("Elapsed time: " .. deltaTime)
-->  Elapsed time: 0.044425600033719 (actual number may vary)