# V795. Size of the 'time_t' type is not 64 bits. After the year 2038, the program will work incorrectly.

The analyzer has detected that a program uses 32-bit data types to store time. This issue will affect those programs that use data types representing the number of seconds elapsed since January 1-st, 1970. After January 19-th, 2038, such programs will no longer be able to represent dates correctly. It is recommended that you use 64-bit types to store time.

The size of the 'time_t' type is not specified by the C/C++ standard, so it can be defined differently depending on the platform and the project's settings:

    typedef /* unspecified */ time_t;

In older versions of Visual C++, the 'time_t' type was 32-bit in 32-bit Windows versions. Starting with Visual C++ 2005, it is a 64-bit integer by default. Modern Visual C++ versions allow you to force the use of the 32-bit version of 'time_t' by using the '_USE_32BIT_TIME_T' directive. You should discard this directive wherever possible and use the 64-bit 'time_t' type instead.

In Linux, 'time_t' is 64-bit only in 64-bit versions of the operating system. Sadly, 32-bit Linux systems do not provide any regular means to make it 64-bit at present. If that is your case, consider replacing 'time_t' with third-party solutions.

References:

- 2038: only 21 years away
- Year 2038 problem
- https://msdn.microsoft.com/en-us/library/w4ddyt9h.aspx