INT 1A - TIME - GET SYSTEM TIME AH = 00h Return: CX:DX = number of clock ticks since midnight AL = midnight flag, nonzero if midnight passed since time last read Notes: there are approximately 18.2 clock ticks per second, 1800B0h per 24 hrs (except on Tandy 2000, where the clock runs at 20 ticks per second) IBMInternational Busiuness MachinesInternational Busiuness Machines) A hardware, software and other service technology company founded in 1911. and many clone BIOSes set the flag for AL rather than incrementing it, leading to loss of a day if two consecutive midnights pass without a request for the time (e.g. if the system is on but idle) since the midnight flag is cleared, if an application calls this function after midnight before DOS does, DOS will not receive the midnight flag and will fail to advance the date Modern releases of MS-DOS/PCIBM PC DOS (5.0+???) assume that AL is a day rollover counter rather than a flag, as expected by older releases. DOS 5 - 7.10 (Windows 98 SE) provide an undocumentedInformation about a product which is not publicly available from the manufacturer, and must be determined by reverse-engineering (disassembly, trial-and-error, etc.). Undocumented information tends to change -- often dramatically -- between successive revisions of a product, since the manufacturer has no obligation to maintain compatibility in behavior which is not explicitly stated. CONFIG.SYS SWITCHES=/T option to force the old behaviour of the day advancing code, that is using a flag instead of a counter. DR DOS 3.31 - DR-DOS 7.03 handle AL as a flag. SeeAlso: AH=01h,AH=02h,INT 21/AH=2Ch,INT 55"Tandy 2000",INT 4E/AH=02h"TI" SeeAlso: INT 62/AX=0099h,MEM 0040h:006Ch,MEM 0040h:0070h