system.date() and system.time()

[kroggen]

I am reviewing some functions that are not public yet to make them public (on documentation) soon

This is a place to discuss the functions system.date() and system.time()

[kroggen]

The above 2 functions are located on system_module.c

Apart from those, similar functions are on Aergo's LuaJIT (the module is disabled, but the functions are there)

Maybe the lib_os.c can be removed from Aergo's LuaJIT, or its content could be made unaccessible using some #ifdef

[kroggen]

Another thing to test is if there is any format specifier for date/time that uses local settings

The result must always be deterministic, regardless of location

[kroggen]

Many common modifiers are locale-dependent. Here are some examples:

%a: Abbreviated weekday name.
%A: Full weekday name.
%b: Abbreviated month name.
%B: Full month name.
%c: Local date and time representation.
%p: Either "AM" or "PM" based on the given time value. However, not all locales recognize this result.
%x: Local date representation.
%X: Local time representation.

[kroggen]

Here is the full list:

The specifiers marked with an asterisk (*) are locale-dependent

specifier	Replaced by	Example
%a	Abbreviated weekday name *	Thu
%A	Full weekday name *	Thursday
%b	Abbreviated month name *	Aug
%B	Full month name *	August
%c	Date and time representation *	Thu Aug 23 14:55:02 2001
%C	Year divided by 100 and truncated to integer (00-99)	20
%d	Day of the month, zero-padded (01-31)	23
%D	Short MM/DD/YY date, equivalent to %m/%d/%y	08/23/01
%e	Day of the month, space-padded ( 1-31)	23
%F	Short YYYY-MM-DD date, equivalent to %Y-%m-%d	2001-08-23
%g	Week-based year, last two digits (00-99)	01
%G	Week-based year	2001
%h	Abbreviated month name * (same as %b)	Aug
%H	Hour in 24h format (00-23)	14
%I	Hour in 12h format (01-12)	02
%j	Day of the year (001-366)	235
%m	Month as a decimal number (01-12)	08
%M	Minute (00-59)	55
%n	New-line character ('\n')
%p	AM or PM designation	PM
%r	12-hour clock time *	02:55:02 pm
%R	24-hour HH:MM time, equivalent to %H:%M	14:55
%S	Second (00-61)	02
%t	Horizontal-tab character ('\t')
%T	ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S	14:55:02
%u	ISO 8601 weekday as number with Monday as 1 (1-7)	4
%U	Week number with the first Sunday as the first day of week one (00-53)	33
%V	ISO 8601 week number (01-53)	34
%w	Weekday as a decimal number with Sunday as 0 (0-6)	4
%W	Week number with the first Monday as the first day of week one (00-53)	34
%x	Date representation *	08/23/01
%X	Time representation *	14:55:02
%y	Year, last two digits (00-99)	01
%Y	Year	2001
%z	ISO 8601 offset from UTC in timezone (1 minute=1, 1 hour=100)If timezone cannot be determined, no characters	+100
%Z	Timezone name or abbreviation *If timezone cannot be determined, no characters	CDT
%%	A % sign	%

[kroggen]

Here are the specifiers that are deterministic (not locale-dependent)

specifier	Replaced by	Example
%c	Date and time representation (modified)	2001-08-23 14:55:02
%C	Year divided by 100 and truncated to integer (00-99)	20
%d	Day of the month, zero-padded (01-31)	23
%D	Short MM/DD/YY date, equivalent to %m/%d/%y	08/23/01
%e	Day of the month, space-padded ( 1-31)	23
%F	Short YYYY-MM-DD date, equivalent to %Y-%m-%d	2001-08-23
%g	Week-based year, last two digits (00-99)	01
%G	Week-based year	2001
%H	Hour in 24h format (00-23)	14
%I	Hour in 12h format (01-12)	02
%j	Day of the year (001-366)	235
%m	Month as a decimal number (01-12)	08
%M	Minute (00-59)	55
%n	New-line character ('\n')
%p	AM or PM designation	PM
%R	24-hour HH:MM time, equivalent to %H:%M	14:55
%S	Second (00-61)	02
%t	Horizontal-tab character ('\t')
%T	ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S	14:55:02
%u	ISO 8601 weekday as number with Monday as 1 (1-7)	4
%U	Week number with the first Sunday as the first day of week one (00-53)	33
%V	ISO 8601 week number (01-53)	34
%w	Weekday as a decimal number with Sunday as 0 (0-6)	4
%W	Week number with the first Monday as the first day of week one (00-53)	34
%y	Year, last two digits (00-99)	01
%Y	Year	2001
%%	A % sign	%

[kroggen]

According to this source the %p modifier (AM/PM) depends on locale also. So it should be removed.

With that, it makes sense to not support %I as well (12-hour format)

[kroggen]

We can also remove %t and %n as these can be replaced with \t and \n on Lua

[kroggen]

The functions system.date() and system.time() have a field isdst used to mark Daylight Saving Time

But the time used on blockchain is always UTC. There is no local time supported, because all the nodes must return the same value regardless of their location.

So it appears reasonable to remove the isdst field from these functions

They are here and here

Is there any remark regarding this?

[hayarobi]

I think nearly all format specifiers can be enabled if we stick environments; locale to en (en_US?) and timezone to UTC, though I am only using ISO8601 format.

[kroggen]

The question is if they are really needed on chain. I suspect that the conversion from an UTC time can be made on client side, so it can use any locale and timezone. The chain can limit its support for UTC only.

The above is for cases when we read from blockchain.

There is one case that it would be good to have local support: when sending transactions and signing on hardware wallet, for example. If the user see one date on the dApp/browser and then it would see another date/time (UTC) when signing.

For this case it could support adding a timezone to the datetime, like 2023-11-13 10:24:30 -03:00

[kroggen]

But the above can be done in the smart contract, by parsing the date, getting the time zone, and applying the difference to the timestamp