C wiki - struct tm

[Kenneth Brody]

http://alien.dowling.edu/~rohit/wiki/index.php/C_Programming#Standard_Library

Q: How are months of a year numbered in C?

Answer makes reference to "the Standard specifies struct tm". Does the
C standard actually define struct tm, or is it Posix that defines it?

--
+-------------------------+--------------------+-----------------------------+
| Kenneth J. Brody | www.hvcomputer.com | |
| kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer.h> |
+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:[email protected]>

 

[Eric Sosman]

http://alien.dowling.edu/~rohit/wiki/index.php/C_Programming#Standard_Library

Q: How are months of a year numbered in C?

Answer makes reference to "the Standard specifies struct tm". Does the
C standard actually define struct tm, or is it Posix that defines it?

Section 7.23.1, paragraph 4.

 

[Ben Pfaff]

Q: How are months of a year numbered in C?

Answer makes reference to "the Standard specifies struct tm". Does the
C standard actually define struct tm, or is it Posix that defines it?

It is in the C standard. See e.g. C99 7.23.1 paragraphs 3 and 4.

 

[Simon Biber]

http://alien.dowling.edu/~rohit/wiki/index.php/C_Programming#Standard_Library

Q: How are months of a year numbered in C?

Answer makes reference to "the Standard specifies struct tm". Does the
C standard actually define struct tm, or is it Posix that defines it?

The C standard defines struct tm as follows:

7.23 Date and time <time.h>
7.23.1 Components of Time
....
4 The range and precision of times representable in clock_t and
time_t are implementation-defined. The tm structure shall
contain at least the following members, in any order. The
semantics of the members and their normal ranges are expressed
in the comments.

int tm_sec; // seconds after the minute — [0, 60]
int tm_min; // minutes after the hour — [0, 59]
int tm_hour; // hours since midnight — [0, 23]
int tm_mday; // day of the month — [1, 31]
int tm_mon; // months since January — [0, 11]
int tm_year; // years since 1900
int tm_wday; // days since Sunday — [0, 6]
int tm_yday; // days since January 1 — [0, 365]
int tm_isdst; // Daylight Saving Time flag

The value of tm_isdst is positive if Daylight Saving Time is
in effect, zero if Daylight Saving Time is not in effect, and
negative if the information is not available.

 

[Spiro Trikaliotis]

Hello,

int tm_sec; // seconds after the minute — [0, 60]
int tm_min; // minutes after the hour — [0, 59]

Is tm_sec really from 0 to 60 (including)? I do not see the sense of it
in contrast to all the others (0.59 for minutes, 0..23 for hour, ...)

What is the rationale behind this? Does it have anything to do with leap
seconds?

Curious,
Spiro.

 

[Stephen Hildrey]

Is tm_sec really from 0 to 60 (including)? I do not see the sense of it
in contrast to all the others (0.59 for minutes, 0..23 for hour, ...)

What is the rationale behind this? Does it have anything to do with leap
seconds?

Yes.

 

[Dik T. Winter]

> > int tm_sec; // seconds after the minute — [0, 60]
> > int tm_min; // minutes after the hour — [0, 59]

>
> Is tm_sec really from 0 to 60 (including)? I do not see the sense of it
> in contrast to all the others (0.59 for minutes, 0..23 for hour, ...)
>
> What is the rationale behind this? Does it have anything to do with leap
> seconds?

It has everything to do with leap seconds.

 

[CBFalconer]

int tm_sec; // seconds after the minute — [0, 60]
int tm_min; // minutes after the hour — [0, 59]

Is tm_sec really from 0 to 60 (including)? I do not see the sense
of it in contrast to all the others (0.59 for minutes, 0..23 for
hour, ...)

What is the rationale behind this? Does it have anything to do
with leap seconds?

Precisely. i.e. yes.