What is the best way to get Unix milliseconds in C?
Use clock_gettime(CLOCK_REALTIME, &ts) and compute ts.tv_sec * 1000 + ts.tv_nsec / 1000000 into a 64-bit integer.
C Get Unix Timestamp in Milliseconds (2026)
If you searched for c get unix timestamp, you likely need a 13-digit epoch value for logs, telemetry, or event ordering. In 2026, the reliable C pattern is to read clock_gettime(CLOCK_REALTIME) and convert nanoseconds to milliseconds with explicit integer math.
Keep the result as a 64-bit integer and pass UTC epoch values across services. This keeps C producers consistent with JavaScript, Go, and SQL consumers and prevents hidden timezone bugs during aggregation.
Copy-ready C snippet
#include <time.h> #include <stdint.h> struct timespec ts; clock_gettime(CLOCK_REALTIME, &ts); int64_t epoch_ms = (int64_t)ts.tv_sec * 1000LL + ts.tv_nsec / 1000000LL;
Related EpochConverter pages
For the base C implementation, read C get Unix timestamp in 2026. For language-wide examples, open Unix timestamp in C. To validate seconds/milliseconds conversions, use epoch seconds to milliseconds.
Need instant two-way conversion while testing? Open the main epoch converter tool.
Related developer tool
If this timestamp code runs on a job schedule, verify cron timing with Cron Expression Builder.
Frequently Asked Questions
Should I use time(NULL) for milliseconds?
time(NULL) returns whole seconds only. Use clock_gettime when you need millisecond precision.
How do I avoid integer overflow for Unix milliseconds?
Store the value in a signed 64-bit type like long long or int64_t. Avoid 32-bit int for timestamp math.
Are Unix milliseconds timezone-dependent?
No. The raw Unix value is UTC-based and timezone-neutral. Convert to local time only when rendering UI output.