Messages from the Ether: Representing time in C, C++, SQL, MFC, and Java

25 April 2005

Representing time in C, C++, SQL, MFC, and Java

[ posted in Programming ]

Options available in representing date and time values:

18 Jan 2006: Added java.util.Date

5 Apr 2006: Added Data column for types

(Links are to MSDN unless otherwise noted.)

Data Representations

Type	Domain	Header	Data
tm	C (struct)	time.h	tm_sec - Seconds after minute (0 – 59). tm_min - Minutes after hour (0 – 59). tm_hour - Hours after midnight (0 – 23). tm_mday - Day of month (1 – 31). tm_mon - Month (0 – 11; January = 0). tm_year - Year (current year minus 1900). tm_wday - Day of week (0 – 6; Sunday = 0). tm_yday - Day of year (0 – 365; January 1 = 0). tm_isdst - Positive value if daylight saving time is in effect; 0 if daylight saving time is not in effect; negative value if status of daylight saving time is unknown.
time_t, __time64_t	C (long)	time.h
SYSTEMTIME	Win32 (C struct)	winbase.h	wYear - The current year. wMonth - The current month; January is 1. wDayOfWeek - The current day of the week; Sunday is 0, Monday is 1, and so on. wDay - The current day of the month. wHour - The current hour. wMinute - The current minute. wSecond - The current second. wMilliseconds - The current millisecond.
FILETIME	Win32 (C struct)	winbase.h	dwLowDateTime - Specifies the low 32 bits of the file time. wHighDateTime - Specifies the high 32 bits of the file time.
DATE	COM (double)	wtypes.h
DBTIMESTAMP	COM (C struct)	oledb.h	year - The year (0 to 9999) is measured from 0 A.D. month - The month ranges from 1 to 12 representing January through December. day - The day ranges from 1 to a maximum of 31, depending on the number of days in the month. hour - The hour ranges from 0 to 23. minute - The minute ranges from 0 to 59. second - The second ranges from 0 to 59. fraction - The fraction represents billionths of a second ranging from 0 to 999,999,999.
CTime	MFC (class, stored as time_t member)	afx.h
COleDateTime	MFC (class, stored as DATE member)	afxdisp.h
java.util.Date	Java

Conversion

From Types -> To Types V	tm	time_t, __time64_t	SYSTEM TIME	FILE TIME	DATE	DBTIME STAMP	CTime	COle DateTime	java.util. Date
tm		gmtime, localtime, _gmtime64, _localtime64					X
time_t, __time64_t	mktime, _mktime64	time, _time64 (current system time)					X		Date. getTime() / 1000
SYSTEM TIME				FileTime ToSystemTime
FILETIME			SystemTime ToFileTime
DATE
DBTIME STAMP
CTime		X	X	X		X
COle DateTime		X	X	X	X	X
java.util. Date		new Date(time_t * 1000)

Limits

SQL information taken from How to search for date and time values using Microsoft SQL Server 2000 by Bryan Syverson and MySQL Reference Manual :: 11.3.1 The DATETIME, DATE, and TIMESTAMP Types.

Type	Minimum (YYYY-MM-DD)	Maximum (YYYY-MM-DD)	Precision
SQL datetime	1753-01-01 (SQL Server), 1000-01-01 (MySQL)	9999-12-31	To the nearest 3.33 milliseconds
SQL smalldatetime	1900-01-01	2079-06-06 23:59 (1 minute until midnight)	To the nearest minute
time_t/tm, __time64_t	1970-01-01 00:00:00	2038-01-18 19:14:07, 3000-12-31 23:59:59	seconds from the minimum time
FILETIME	1601-01-01
DATE			Zero is 1899-12-31 00:00:00
CTime	1970-01-01	2038-01-18
COleDateTime	0100-01-01	9999-12-31
java.util.Date			zero is 1970-01-01 00:00:00, milliseconds from zero

TODO: Add relevant functions, facets, and boost utilities.

Keywords

[ posted on 25 April 2005 at 10:41:17 AM ]

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