converting long long to date

[peterjanovsky]

well i have a value which is a long long (5245738275906267986), at least what i gather from my internet research

lower limit
−9,223,372,036,854,775,808

upper limit
9,223,372,036,854,775,807

the following produces unexpected output.

long long x = 5245738275906267986;
time_t dt = x;
printf("dt: %s\n", ctime(&dt));

how would i properly convert the value to time_t

[MK27]

You wouldn't. That is several thousand years into the future.

Where are you getting this value from?

[nonoob]

As MK27 implied, timestamp is in seconds. So your huge number is billions of years in the future. If the value is in microseconds it's still too huge.

At about a billion seconds is where the number would be to represent today. That's how many seconds are in 30 years starting from 1980.

[peterjanovsky]

the value is a DateTime converted to an int64 value in a C# program. the C# program then sends the value to a C application where it needs to be converted to a DateTime to check the authenticity of the call, along with a few other values contained within a hashed string.

is the issue that the value is generated within C#?

[MK27]

The issue is that "5245738275906267986" is not a valid date. If it were a number of seconds, it would be more than 166341269530 years. Is this a special Galactic calender or something?

A C# DateTime is an object. What value from it did you convert to an int64?

Basically someone has mangled this data.

[peterjanovsky]

hmmmm, maybe C# itself modifies the value.

here is the C# code which creates the value
long binValue = DateTime.UtcNow.ToBinary()

here is the C# code which decodes the value
DateTime.FromBinary(binValue);

the portion of the code which converts the binValue to a DateTime needs to be happen in C. what is the best way to approach this conversion?

[tabstop]

That number is not necessarily (not at all?) the number of ticks, as it also contains the information about Kind (according to DateTime.ToBinary Method (System) at any rate). So the question is "why does it need to happen in C, and if it does, why don't you get 'real' data out of the thing (like the number of ticks)?"