Date: Date and Time Printing, Parsing and Manipulation

Utility functions to handle date and time (adjusting, getting the current date, printing the date and time, etc.) More...

Files
file	gnc-date.h
	Date and Time handling routines.

Data Structures
struct	Time64

Macros
#define	MAX_DATE_LENGTH   34
	The maximum length of a string created by the date printers.
#define	QOF_UTC_DATE_FORMAT   "%Y-%m-%dT%H:%M:%SZ"
	Constants. More...
#define	DATE_FORMAT_FIRST   QOF_DATE_FORMAT_US
#define	DATE_FORMAT_LAST   QOF_DATE_FORMAT_UTC

Typedefs
typedef gint64	time64
	Most systems that are currently maintained, including Microsoft Windows, BSD-derived Unixes and Linux, support 64-bit time_t even on 32-bit architectures. More...

Enumerations
enum	QofDateFormat {   QOF_DATE_FORMAT_US, QOF_DATE_FORMAT_UK, QOF_DATE_FORMAT_CE, QOF_DATE_FORMAT_ISO,   QOF_DATE_FORMAT_LOCALE, QOF_DATE_FORMAT_UTC, QOF_DATE_FORMAT_CUSTOM, QOF_DATE_FORMAT_UNSET }
	Enum for determining a date format. More...
enum	QofDateCompletion { QOF_DATE_COMPLETION_THISYEAR, QOF_DATE_COMPLETION_SLIDING }
	Enum for date completion modes (for dates entered without year) More...
enum	GNCDateMonthFormat { GNCDATE_MONTH_NUMBER, GNCDATE_MONTH_ABBREV, GNCDATE_MONTH_NAME }
	This is how to format the month, as a number, an abbreviated string, or the full name.

Functions
struct tm *	gnc_localtime (const time64 *secs)
	fill out a time struct from a 64-bit time value. More...
struct tm *	gnc_localtime_r (const time64 *secs, struct tm *time)
	fill out a time struct from a 64-bit time value adjusted for the current time zone. More...
struct tm *	gnc_gmtime (const time64 *secs)
	fill out a time struct from a 64-bit time value More...
gint	gnc_start_of_week (void)
	returns an integer corresponding to locale start of week More...
time64	gnc_mktime (struct tm *time)
	calculate seconds from the epoch given a time struct More...
time64	gnc_timegm (struct tm *time)
	calculate seconds from the epoch given a time struct More...
gchar *	gnc_ctime (const time64 *secs)
	Return a string representation of a date from a 64-bit time value. More...
time64	gnc_time (time64 *tbuf)
	get the current time More...
gdouble	gnc_difftime (const time64 secs1, const time64 secs2)
	Find the difference in seconds between two time values (deprecated) More...
void	gnc_tm_free (struct tm *time)
	free a struct tm* created with gnc_localtime() or gnc_gmtime() More...
time64	time64CanonicalDayTime (time64 t)
	convert a time64 on a certain day (localtime) to the time64 representing midday on that day. More...
time64	gdate_to_time64 (GDate d)
	Turns a GDate into a time64, returning the first second of the day.
time64	gnc_dmy2time64 (gint day, gint month, gint year)
	Convert a day, month, and year to a time64, returning the first second of the day.
time64	gnc_dmy2time64_neutral (gint day, gint month, gint year)
	Converts a day, month, and year to a time64 representing 11:00:00 UTC 11:00:00 UTC falls on the same time in almost all timezones, the exceptions being the +13, +14, and -12 timezones used by countries along the International Date Line. More...
time64	gnc_dmy2time64_end (gint day, gint month, gint year)
	Same as gnc_dmy2time64, but last second of the day.
time64	gnc_iso8601_to_time64_gmt (const gchar *)
	The gnc_iso8601_to_time64_gmt() routine converts an ISO-8601 style date/time string to time64. More...
gchar *	gnc_time64_to_iso8601_buff (time64, char *buff)
	The gnc_time64_to_iso8601_buff() routine takes the input UTC time64 value and prints it as an ISO-8601 style string. More...

Variables
const char *	gnc_default_strftime_date_format
	The default date format for use with strftime. More...

GValue
GType	time64_get_type (void)
#define	GNC_TYPE_TIME64   (time64_get_type ())

String / DateFormat conversion.
const gchar *	gnc_date_dateformat_to_string (QofDateFormat format)
	The string->value versions return FALSE on success and TRUE on failure.
gboolean	gnc_date_string_to_dateformat (const gchar *format_string, QofDateFormat *format)
	Converts the date format to a printable string. More...
const gchar *	gnc_date_monthformat_to_string (GNCDateMonthFormat format)
gboolean	gnc_date_string_to_monthformat (const gchar *format_string, GNCDateMonthFormat *format)
	Converts the month format to a printable string. More...
char *	gnc_print_time64 (time64 time, const char *format)
	print a time64 as a date string per format More...

GDate time64 setters
GDate *	gnc_g_date_new_today (void)
	Returns a newly allocated date of the current clock time, taken from time(2). More...
void	gnc_gdate_set_today (GDate *gd)
	Set a GDate to the current day. More...
void	gnc_gdate_set_time64 (GDate *gd, time64 time)
	Set a GDate to a time64. More...

Detailed Description

Utility functions to handle date and time (adjusting, getting the current date, printing the date and time, etc.)

Overall, this file is quite a mess.

An important note about time-keeping: The general goal of any program that works with numeric time values SHOULD BE to always stores and use UNIVERSAL TIME internally. Universal time is the 'one true time' that is independent of one's location on planet Earth. It is measured in seconds from midnight January 1, 1970 in localtime-Greenwich (GMT). If one wants to display the local time, then the display-print routine should make all final tweaks to print the local time. The local time must not be kept as a numeric value anywhere in the program. If one wants to parse a user's input string as if it were local time, then the output of the parse routine MUST BE universal time. A sane program must never ever store (to file or db) a time that is not Universal Time. Break these rules, and you will rue the day...

Warning

HACK ALERT – the scan and print routines should probably be moved to somewhere else. The engine really isn't involved with things like printing formats. This is needed mostly by the GUI and so on. If a file-io backend needs date handling, it should do it itself, instead of depending on the routines here.

(to be renamed qofdate.h in libqof2.)

Author

Copyright (C) 1997 Robin D. Clark rclar.nosp@m.k@cs.nosp@m..hmc..nosp@m.edu

Copyright (C) 1998-2001,2003 Linas Vepstas linas.nosp@m.@lin.nosp@m.as.or.nosp@m.g

Macro Definition Documentation

QOF_UTC_DATE_FORMAT

#define QOF_UTC_DATE_FORMAT   "%Y-%m-%dT%H:%M:%SZ"

Constants.

UTC date format string.

Time zone independent, date and time inclusive, as used in the QSF backend. The T and Z characters are from xsd:dateTime format in coordinated universal time, UTC. You can reproduce the string from the GNU/Linux command line using the date utility: date -u +Y-m-dTH:M:SZ = 2004-12-12T23:39:11Z The datestring must be time zone independent and include all specified fields. Remember to use gmtime() NOT localtime()!

Definition at line 119 of file gnc-date.h.

Typedef Documentation

time64

typedef gint64 time64

Most systems that are currently maintained, including Microsoft Windows, BSD-derived Unixes and Linux, support 64-bit time_t even on 32-bit architectures.

See https://en.wikipedia.org/wiki/Year_2038_problem

For practical reasons – as not all have made the transition to 64-bit – we define our own 64-bit time type.

Definition at line 87 of file gnc-date.h.

Enumeration Type Documentation

QofDateCompletion

enum QofDateCompletion

Enum for date completion modes (for dates entered without year)

Enumerator
QOF_DATE_COMPLETION_THISYEAR	use current year
QOF_DATE_COMPLETION_SLIDING	use sliding 12-month window

Definition at line 138 of file gnc-date.h.

{
    QOF_DATE_COMPLETION_THISYEAR, 
    QOF_DATE_COMPLETION_SLIDING,  
} QofDateCompletion;

QofDateFormat

enum QofDateFormat

Enum for determining a date format.

Enumerator
QOF_DATE_FORMAT_US	United states: mm/dd/yyyy.
QOF_DATE_FORMAT_UK	Britain: dd/mm/yyyy.
QOF_DATE_FORMAT_CE	Continental Europe: dd.mm.yyyy.
QOF_DATE_FORMAT_ISO	ISO: yyyy-mm-dd.
QOF_DATE_FORMAT_LOCALE	Take from locale information.
QOF_DATE_FORMAT_UTC	UTC: 2004-12-12T23:39:11Z.
QOF_DATE_FORMAT_CUSTOM	Used by the check printing code.
QOF_DATE_FORMAT_UNSET	No Fancy Date Format, use Global.

Definition at line 122 of file gnc-date.h.

{
    QOF_DATE_FORMAT_US,       
    QOF_DATE_FORMAT_UK,       
    QOF_DATE_FORMAT_CE,       
    QOF_DATE_FORMAT_ISO,      
    QOF_DATE_FORMAT_LOCALE,   
    QOF_DATE_FORMAT_UTC,      
    QOF_DATE_FORMAT_CUSTOM,   
    QOF_DATE_FORMAT_UNSET     
} QofDateFormat;

Function Documentation

gnc_ctime()

gchar* gnc_ctime

(

const time64 *

secs

)

Return a string representation of a date from a 64-bit time value.

Parameters

secs	Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment)

Returns

A string, which must be freed with g_free(), representing the date in the following format: Thu Nov 24 18:22:48 1986
\0 This is equivalent to the strftime format a b H:M:S Y.

Definition at line 255 of file gnc-date.cpp.

{
    return gnc_print_time64(*secs, "%a %b %d %H:%M:%S %Y");
}

gnc_date_string_to_dateformat()

gboolean gnc_date_string_to_dateformat	(	const gchar *	format_string,
		QofDateFormat *	format
	)

Converts the date format to a printable string.

Note the reversed return values!

Returns

FALSE on success, TRUE on failure.

gnc_date_string_to_monthformat()

gboolean gnc_date_string_to_monthformat	(	const gchar *	format_string,
		GNCDateMonthFormat *	format
	)

Converts the month format to a printable string.

Note the reversed return values!

Returns

FALSE on success, TRUE on failure.

gnc_difftime()

gdouble gnc_difftime	(	const time64	secs1,
		const time64	secs2
	)

Find the difference in seconds between two time values (deprecated)

Parameters

secs1	The first time value, in Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment)
secs2	The second time value, in Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment)

Returns

The difference in seconds between secs1 and secs2. If secs2 is later than secs1 the value will be negative.

Definition at line 271 of file gnc-date.cpp.

{
    PWARN ("gnc_difftime is deprecated");
    return (double)secs1 - (double)secs2;
}

gnc_dmy2time64_neutral()

time64 gnc_dmy2time64_neutral	(	gint	day,
		gint	month,
		gint	year
	)

Converts a day, month, and year to a time64 representing 11:00:00 UTC 11:00:00 UTC falls on the same time in almost all timezones, the exceptions being the +13, +14, and -12 timezones used by countries along the International Date Line.

Since users in those timezones would see dates immediately change by one day, the function checks the current timezone for those changes and adjusts the UTC time so that the date will be consistent.

gnc_g_date_new_today()

GDate* gnc_g_date_new_today

(

void

)

Returns a newly allocated date of the current clock time, taken from time(2).

The caller must g_date_free() the object afterwards.

Definition at line 1225 of file gnc-date.cpp.

{
    GncDate gncd;
    auto ymd = gncd.year_month_day();
    auto month = static_cast<GDateMonth>(ymd.month);
    auto result = g_date_new_dmy (ymd.day, month, ymd.year);
    g_assert(g_date_valid (result));
    return result;
}

gnc_gdate_set_time64()

void gnc_gdate_set_time64	(	GDate *	gd,
		time64	time
	)

Set a GDate to a time64.

Parameters

gd	the date to act on
time	the time to set it to.

Definition at line 1244 of file gnc-date.cpp.

{
    struct tm tm;
    gnc_localtime_r(&time, &tm);
    g_date_set_dmy (gd, tm.tm_mday,
                    static_cast<GDateMonth>(tm.tm_mon + 1),
                    tm.tm_year + 1900);
}

gnc_gdate_set_today()

void gnc_gdate_set_today

(

GDate *

gd

)

Set a GDate to the current day.

Parameters

gd	The date to act on

Definition at line 1236 of file gnc-date.cpp.

{
    GDate *today = gnc_g_date_new_today ();
    g_date_set_julian (gd, g_date_get_julian (today));
    g_date_free (today);
}

gnc_gmtime()

struct tm* gnc_gmtime

(

const time64 *

secs

)

fill out a time struct from a 64-bit time value

Parameters

secs	Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment)

Returns

A struct tm*, allocated on the heap. Must be freed with gnc_tm_free() The time is UTC.

Definition at line 177 of file gnc-date.cpp.

{
    try
    {
        GncDateTime gncdt(*secs);
        auto time = static_cast<struct tm*>(calloc(1, sizeof(struct tm)));
        *time = gncdt.utc_tm();
        return time;
    }
    catch(std::invalid_argument&)
    {
        return nullptr;
    }

}

gnc_iso8601_to_time64_gmt()

time64 gnc_iso8601_to_time64_gmt

(

const gchar *

)

The gnc_iso8601_to_time64_gmt() routine converts an ISO-8601 style date/time string to time64.

Please note that ISO-8601 strings are a representation of Universal Time (UTC), and as such, they 'store' UTC. To make them human readable, they show time zone information along with a local-time string. But fundamentally, they are UTC. Thus, this routine takes a UTC input, and returns a UTC output.

For example: 1998-07-17 11:00:00.68-0500 is 680 milliseconds after 11 o'clock, central daylight time It is also 680 milliseconds after 16:00:00 hours UTC.

Returns

The universal time.

XXX Caution: this routine does not handle strings that specify times before January 1 1970.

gnc_localtime()

struct tm* gnc_localtime

(

const time64 *

secs

)

fill out a time struct from a 64-bit time value.

Parameters

secs	Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment).

Returns

A struct tm*, allocated on the heap. Must be freed with gnc_tm_free(). The time is adjusted for the current local time zone.

Definition at line 102 of file gnc-date.cpp.

{
    auto time = static_cast<struct tm*>(calloc(1, sizeof(struct tm)));
    if (gnc_localtime_r (secs, time) == nullptr)
    {
        gnc_tm_free (time);
        return nullptr;
    }
    return time;
}

gnc_localtime_r()

struct tm* gnc_localtime_r	(	const time64 *	secs,
		struct tm *	time
	)

fill out a time struct from a 64-bit time value adjusted for the current time zone.

Parameters

secs	Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment)
time	A struct tm* for the function to fill. The time is adjusted for the current local time zone.

Definition at line 114 of file gnc-date.cpp.

{
    try
    {
        *time = static_cast<struct tm>(GncDateTime(*secs));
        return time;
    }
    catch(std::invalid_argument&)
    {
        return nullptr;
    }
}

gnc_mktime()

time64 gnc_mktime

(

struct tm *

time

)

calculate seconds from the epoch given a time struct

Parameters

time	A struct tm* containing the date-time information. The time is understood to be in the current local time zone.

Returns

Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment).

Definition at line 218 of file gnc-date.cpp.

{
    try
    {
        normalize_struct_tm (time);
        GncDateTime gncdt(*time);
        *time = static_cast<struct tm>(gncdt);
        return static_cast<time64>(gncdt);
    }
    catch(std::invalid_argument&)
    {
        return 0;
    }
}

gnc_print_time64()

char* gnc_print_time64	(	time64	time,
		const char *	format
	)

print a time64 as a date string per format

Parameters

time	The time64 to print
format	A date format conforming to the strftime format rules.

Returns

a raw heap-allocated char* which must be freed.

Definition at line 369 of file gnc-date.cpp.

{
    try
    {
        GncDateTime gncdt(time);
        auto sstr = gncdt.format(format);
        //ugly C allocation so that the ptr can be freed at the other end
        char* cstr = static_cast<char*>(malloc(sstr.length() + 1));
        memset(cstr, 0, sstr.length() + 1);
        strncpy(cstr, sstr.c_str(), sstr.length());
        return cstr;
    }
    catch(std::runtime_error& err)
    {
        PWARN("Error processing time64 %" PRId64 ": %s", time, err.what());
        return nullptr;
    }
    catch(std::logic_error& err)
    {
        PWARN("Error processing time64 %" PRId64 ": %s", time, err.what());
        return nullptr;
    }
}

gnc_start_of_week()

gint gnc_start_of_week

(

void

)

returns an integer corresponding to locale start of week

Returns

An integer 1=Sunday, 2=Monday etc. If error, return 0.

Definition at line 194 of file gnc-date.cpp.

{
    /* icu's day of week is 1 based. Using 0 here to mean unset or error while setting */
    static int cached_result = 0;

    if (!cached_result)
    {
        UErrorCode err = U_ZERO_ERROR;
        auto cal = icu::Calendar::createInstance (err);
        if (!cal)
        {
            PERR("ICU error: %s\n", u_errorName (err));
            return 0;
        }

        /* 1 for sunday, 2 for monday, etc. */
        cached_result = cal->getFirstDayOfWeek (err);
        delete cal;
    }

    return cached_result;
}

gnc_time()

time64 gnc_time

(

time64 *

tbuf

)

get the current time

Parameters

A	time64* which, if not NULL, will be filled in with the same value as is returned.

Returns

Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment)

Definition at line 261 of file gnc-date.cpp.

{
    GncDateTime gncdt;
    auto time = static_cast<time64>(gncdt);
    if (tbuf != nullptr)
        *tbuf = time;
    return time;
}

gnc_time64_to_iso8601_buff()

gchar* gnc_time64_to_iso8601_buff	(	time64	,
		char *	buff
	)

The gnc_time64_to_iso8601_buff() routine takes the input UTC time64 value and prints it as an ISO-8601 style string.

The buffer must be long enough to contain the NULL-terminated string (32 characters + NUL). This routine returns a pointer to the null terminator (and can thus be used in the 'stpcpy' metaphor of string concatenation).

Please note that ISO-8601 strings are a representation of Universal Time (UTC), and as such, they 'store' UTC. To make them human readable, they show time zone information along with a local-time string. But fundamentally, they are UTC. Thus, this routine takes a UTC input, and returns a UTC output.

The string generated by this routine uses the local time zone on the machine on which it is executing to create the time string.

Definition at line 1140 of file gnc-date.cpp.

{
    if (!buff) return nullptr;
    try
    {
        GncDateTime gncdt(time);
        auto sstr = gncdt.format_iso8601();

        memset(buff, 0, sstr.length() + 1);
        strncpy(buff, sstr.c_str(), sstr.length());
        return buff + sstr.length();
    }
    catch(std::logic_error& err)
    {
        PWARN("Error processing time64 %" PRId64 ": %s", time, err.what());
        return buff;
    }
    catch(std::runtime_error& err)
    {
        PWARN("Error processing time64 %" PRId64 ": %s", time, err.what());
        return buff;
    }
}

gnc_timegm()

time64 gnc_timegm

(

struct tm *

time

)

calculate seconds from the epoch given a time struct

Parameters

time	A struct tm* containing the date-time information The time is understood to be utc.

Returns

Seconds since 00:00:00 UTC 01 January 1970 (negative values are seconds before that moment).

Definition at line 234 of file gnc-date.cpp.

{
    try
    {
        normalize_struct_tm(time);
        GncDateTime gncdt(*time);
        *time = static_cast<struct tm>(gncdt);
        time->tm_sec -= gncdt.offset();
        normalize_struct_tm(time);
#ifdef HAVE_STRUcT_TM_GMTOFF
        time->tm_gmtoff = 0;
#endif
        return static_cast<time64>(gncdt) - gncdt.offset();
    }
    catch(std::invalid_argument&)
    {
        return 0;
    }
}

gnc_tm_free()

void gnc_tm_free

(

struct tm *

time

)

free a struct tm* created with gnc_localtime() or gnc_gmtime()

Parameters

time	The struct tm* to be freed.

Definition at line 96 of file gnc-date.cpp.

{
    free(time);
}

time64CanonicalDayTime()

time64 time64CanonicalDayTime

(

time64

t

)

convert a time64 on a certain day (localtime) to the time64 representing midday on that day.

Watch out - this is not the first second of the day, which is returned by various other functions returning a time64.

Definition at line 403 of file gnc-date.cpp.

{
    struct tm tm;
    gnc_localtime_r(&t, &tm);
    gnc_tm_set_day_middle(&tm);
    return gnc_mktime (&tm);
}

Variable Documentation

gnc_default_strftime_date_format

const char* gnc_default_strftime_date_format

The default date format for use with strftime.

Definition at line 73 of file gnc-date.cpp.