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
The value you've given is 36 hex digits, i.e. 18 bytes-worth. That's not an Int64 converted to hex.
Go back to whoever gave you the explanation of the format and ask them to tell you the truth this time :)
EDIT: Okay, next step: find out what that number is actually meant to mean. Ticks since 1970? Millis since AD 1? Do you know what your example string is meant to represent?