Re: [art] Predictable Internet Time

[Joe Touch <[e-mail]>]

On 3/29/2017 9:11 AM, Philip Homburg wrote:
>>> Every time_t value has a specific interpretation as a UTC timestamp.
>> There is an intended correlation between Unix dates and UTC dates, but
>> it isn't exact - the equation is indicated as approximate.
> Quoting the opengroup docs, and this is the last thing I will say
> about POSIX time:

We've all been referring to this.

The problem is that POSIX never defines second, and that this entire
paragraph starts with "a value that approximates".
It also refers to "a Coordinated Universal Time name", that's a data
structure, not an assurance that seconds since epoch actually
synchronizes to UTC.

Joe

> "4.16 Seconds Since the Epoch
> "
> "A value that approximates the number of seconds that have elapsed since the Epoch. A Coordinated Universal Time name (specified in terms of seconds (tm_sec), minutes (tm_min), hours (tm_hour), days since January 1 of the year (tm_yday), and calendar year minus 1900 (tm_year)) is related to a time represented as seconds since the Epoch, according to the expression below.
> "
> "If the year is <1970 or the value is negative, the relationship is undefined. If the year is >=1970 and the value is non-negative, the value is related to a Coordinated Universal Time name according to the C-language expression, where tm_sec, tm_min, tm_hour, tm_yday, and tm_year are all integer types:
> "
> "tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +
> "    (tm_year-70)*31536000 + ((tm_year-69)/4)*86400 -
> "    ((tm_year-1)/100)*86400 + ((tm_year+299)/400)*86400
>
> Feel free to define POSIX time as you wish. This what the opengroup says
> about it.
>