Help me translate long value, expressed in hex, back in to a date/time

Question

I have a date value, which I\'m told is 8 bytes, a single \"long\" (aka int64) value, and converted to hex:

60f347d15798c901

How can I convert

Answer 1

I found another reference which might point to some more relevant information. In this case, a Windows date and time as used in the registry. Apparently these are also stored as 64 bit values.

This is looking a bit more helpful, as it mentions that ending in C?01 is an indicator of this type of date. Note that this is little endian (ie, most significant bytes on the right) so the bytes are in the wrong byte order for hexdec() without reversing them 2 hex digits at a time (ie, start with right-most 2 hex digits, then next two, etc).

And, according to this source,

A single tick represents one hundred nanoseconds or one ten-millionth of a second. The value of this property represents the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001, which represents.

What might trip you up is that unfortunately PHP cannot handle 64 bit integers. It maxes out at 32 bit. Floats will help, but that doesn't stop hexdec() itself from only coping with ints. So it may be complicated to do this math; you may still need to split it into two, then combine them into a float by casting the more significant value to float and multiplying it by 2^32 also cast as float. It's possible that PHP built for 64-bit hardware may not have this limitation, but I don't know for sure.