clock_gettime suddenly not working anymore today, what could be the issue?

My code suddenly not working anymore today, what could be the issue?
Here is the part of the code.

struct timespec tp;
clock_gettime(CLOCK_MONOTONIC, &tp);
int32_t tnow = tp.tv_sec * 1000 + tp.tv_nsec / 1000000;

if (tnow - decoder->last_dumped >= 300) {
    decoder->last_dumped = tnow;
    // it was working before
    ...
}

>Solution :

tv_sec is a signed integer holding seconds, so 1000 * tv_sec will overflow an int32_t. Use int64_t.

Overflow will occur after (1 << 31) milliseconds, which is about 24.8 days.