Date and time library - cppreference.com (original) (raw)

C++ includes support for two types of time manipulation:

• The chrono library, a flexible collection of types that track time with varying degrees of precision (e.g., std::chrono::time_point).
• C-style date and time library (e.g., std::time).

Contents

• 1 Chrono library (since C++11)
  • 1.1 Clocks
  • 1.2 Time point
  • 1.3 Duration
  • 1.4 Time of day (since C++20)
  • 1.5 Calendar (since C++20)
  • 1.6 Time zone (since C++20)
  • 1.7 Literals (since C++14)
  • 1.8 Chrono I/O (since C++20)
• 2 Notes
• 3 C-style date and time library
• 4 Example

[edit] Chrono library (since C++11)

The chrono library defines several main types as well as utility functions and common typedefs:

• clocks
• time points
• durations

[edit] Clocks

A clock consists of a starting point (or epoch) and a tick rate. For example, a clock may have an epoch of January 1, 1970 and tick every second. C++ defines several clock types:

[edit] Time point

A time point is a duration of time that has passed since the epoch of a specific clock.

[edit] Duration

A duration consists of a span of time, defined as some number of ticks of some time unit. For example, "42 seconds" could be represented by a duration consisting of 42 ticks of a 1-second time unit.

[edit] Time of day (since C++20)

hh_mm_ss splits a duration representing time elapsed since midnight into hours, minutes, seconds, and fractional seconds, as applicable. It is primarily a formatting tool.

[edit] Calendar (since C++20)

[edit] Time zone (since C++20)

[edit] Literals (since C++14)

[edit] Chrono I/O (since C++20)

[edit] Notes

[edit] C-style date and time library

Also provided are the C-style date and time functions, such as std::time_t, std::difftime, and CLOCKS_PER_SEC.

[edit] Example

#include #include   long Fibonacci(unsigned n) { return n < 2 ? n : Fibonacci(n - 1) + Fibonacci(n - 2); }   int main() { // Measures and displays an execution time of a function call. const auto start{std::chrono::steady_clock::now()}; const auto fb{Fibonacci(42)}; const auto finish{std::chrono::steady_clock::now()}; const std::chrono::duration elapsed_seconds{finish - start};   std::cout << "Fibonacci(42): " << fb << "\nElapsed time: "; // std::cout << elapsed_seconds.count() << "s\n"; // Before C++20 std::cout << elapsed_seconds << '\n'; // C++20's chrono::duration operator<<   // Prints UTC and local time. const auto tp_utc{std::chrono::system_clock::now()}; std::cout << "Current time 'UTC' is: " << tp_utc << "\n" "Current time 'Local' is: " << std::chrono::current_zone()->to_local(tp_utc) << '\n'; }

Possible output:

Fibonacci(42): 267914296 Elapsed time: 0.728532s Current time 'UTC' is: 2025-02-10 06:22:39.420666960 Current time 'Local' is: 2025-02-10 09:22:39.420666960