I'm creating a mock object to test my application so that it works at the boundary conditions of time. I'm using FILETIME in the Windows SDK.
The link shows the earliest time which is January 1, 1601 (I'm assuming midnight 00:00:00 and both dwLowDateTime and dwHighDateTime are 0x00000000), so I have that. What is the latest possible FILETIME?
My first instinct is to set dwLowDateTime and dwHighDateTime to 0xFFFFFFFF, but then I questioned if that really is a valid time that I need to test, due to where my linked page says the SetFileTime function uses 0xFFFFFFFF to specify that a file's previous access time should be preserved.
Answer
My understanding is that FILETIME was made to represent any valid SYSTEMTIME in 64 bits. If you take the limit of SYSTEMTIME (last millisecond in 30827) then you end up with a FILETIME of 0x7fff35f4f06c58f0 by using SystemTimeToFileTime().
However, if you put 0x7fffffffffffffff into FileTimeToSystemTime() then you will end up in the year 30828, although this date is invalid for SYSTEMTIME. Any larger value (0x8000000000000000 and above) causes FileTimeToSystemTime() to fail.
All in all, I would recommend not to go beyond 0x7fff35f4f06c58f0 in order to stay compatible with SYSTEMTIME.