The great thing about timestamps is that there are so many to choose from. Sometimes, while debugging (or reading incomplete documentation) you’ll find a timestamp and wonder how to convert it into something readable. Here are some tips.<\/p>\n
We will use November 26, 2002 at 7:25p PST as our sample time.<\/p>\n
UNIX timestamps are in seconds since January 1, 1970 UTC. It is a 32-bit number, the only 32-bit number in common use as a timestamp.<\/p>\n
November 26, 2002 at 7:25p PST = 0x3DE43B0C.<\/p>\n
If it’s a 32-bit value starting with “3”, it’s probably a UNIX time. (The “3” era began in 1995 and ends in 2004.)<\/p>\n
To convert these values to something readable, you have several choices.<\/p>\n
The C runtime time_t value is the same as a UNIX timestamp, so you can use the This is the time format used by the C runtime and by the Windows NT event log.<\/p>\n Win32 FILETIME values count 100-nanosecond intervals since January 1, 1600 UTC. It is a 64-bit number.<\/p>\n November 26, 2002 at 7:25p PST = 0x01C295C4:91150E00.<\/p>\n If it’s a 64-bit value starting with “01” and a letter, it’s probably a Win32 FILETIME. The “01A” era began in 1972 and the “01F” era ends in 2057.<\/p>\n To convert these values to something readable, you can use the Warning: Actual .NET content<\/strong> (I’m sorry). CLR System.DateTime values count 100-nanosecond intervals since January 1, 1 UTC. It is a 64-bit number. These aren’t used much yet.<\/p>\n November 26, 2002 at 7:25p PST = 0x08C462CB:FCED3800. (? somebody check my math)<\/p>\n If it’s a 64-bit value starting with “08” and a letter, it’s probably a CLR System.DateTime. The “08A” began in 1970 and the “08F” era ends in 2056.<\/p>\n To convert these values to something readable, construct a System.DateTime object passing the 64-bit time value as the constructor parameter.<\/p>\n The DOS date\/time format is a bitmask:<\/p>\n The year is stored as an offset from 1980. Seconds are stored in two-second increments. (So if the “second” value is 15, it actually represents 30 seconds.)<\/p>\n These values are recorded in local time<\/i>.<\/p>\n November 26, 2002 at 7:25p PST = 0x2D7A9B20.<\/p>\n To convert these values to something readable, convert it to a FILETIME via DosDateTimeToFileTime, then convert the FILETIME to something readable.<\/p>\n The OLE automation date format is a floating point value, counting days since midnight 30 December 1899. Hours and minutes are represented as fractional days.<\/p>\n Often there is no direct conversion between two formats; you will have to go through some intermediary formats.<\/p>\n Let’s see if I can draw a little chart.<\/p>\n I’m not sure that chart actually cleared up anything.<\/p>\n If you allow yourself to use MFC, then there are some more conversions available.<\/p>\n I won’t bother trying to add these (unidirectional) arrows to the chart above.<\/p>\n Brad Abrams’ blog<\/a> followed some of these arrows and produced a cute little formula to convert UNIX time_t directly to System.DateTime<\/a>.<\/p>\n JScript’s Date object constructor can construct from an integer representing milliseconds since 1970. This is the same as UNIX time, just multiplied by 1000.<\/p>\nctime()<\/code> function, for example.<\/p>\nNumber two: The Win32 FILETIME<\/h2>\n
FileTimeToSystemTime()<\/code> function followed by GetDateFormat()<\/code> and GetTimeFormat()<\/code>.<\/p>\nNumber three: The CLR System.DateTime<\/h2>\n
Number four: The DOS date\/time format<\/h2>\n
24 16 8 0\r\n+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+\r\n|Y|Y|Y|Y|Y|Y|Y|M| |M|M|M|D|D|D|D|D| |h|h|h|h|h|m|m|m| |m|m|m|s|s|s|s|s|\r\n+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+\r\n \\___________\/\\________\/\\_________\/ \\________\/\\____________\/\\_________\/\r\n year month day hour minute second\r\n<\/pre>\n
Number five: OLE Automation date format<\/h2>\n
Converting among these formats<\/h2>\n
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Other time formats<\/h2>\n