Standard library header <ctime>

C++

Language

Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Standard Library header files

Language Support
<cstddef> <limits> <climits> <contract>	<cfloat> <cstdint> <new> <version>	<typeinfo> <exception> <initializer_list>	<csignal> <csetjmp> <cstdarg>
Concepts
<concepts>
Diagnostics
<stdexcept>	<cassert>	<cerrno>	<system_error>
General utilities
<utility> <memory> <memory_resource> <scoped_allocator> <compare>	<bitset> <tuple> <optional> <any> <variant>	<type_traits> <ratio> <chrono> <typeindex> <functional>	<ctime> <cstdlib>
Strings
<string> <string_view>	<cctype> <cwctype>	<cwchar> <cuchar>	<cstring> <charconv>
Localization
<locale>	<codecvt>	<clocale>
Containers
<span> <array> <vector>	<deque> <forward_list> <list>	<map> <set> <queue>	<unordered_map> <unordered_set> <stack>
Iterators
<iterator>
Algorithms
<algorithm>	<execution>
Numerics
<complex> <random>	<valarray> <numeric>	<cfenv> <cmath>	<bit>
Input/Output
<iosfwd> <ios> <iomanip> <streambuf>	<istream> <ostream> <iostream>	<sstream> <fstream> <syncstream>	<cstdio> <cinttypes> <strstream>
Regular expressions
<regex>
Filesystem support
<filesystem>
Thread support
<thread> <atomic>	<mutex> <shared_mutex>	<condition_variable> <future>
C compatibility
<ciso646> <cstdalign>	<cstdbool> <ccomplex>	<ctgmath>

This header was originally in the C standard library as <time.h>.

This header is part of the C-style date and time library.

Macro Constants

CLOCKS_PER_SEC	number of processor clock ticks per second (macro constant)
NULL	implementation-defined null pointer constant (macro constant)

Types

clock_t	process running time (typedef)
size_t	unsigned integer type returned by the sizeof operator (typedef)
time_t	time since epoch type (typedef)
tm	calendar time type (class)
timespec (since C++17)	time in seconds and nanoseconds (struct)

Functions

Time manipulation
clock	returns raw processor clock time since the program is started (function)
time	returns the current time of the system as time since epoch (function)
difftime	computes the difference between times (function)
timespec_get (since C++17)	returns the calendar time based on a given time base (function)
Format conversions
ctime	converts a time_t object to a textual representation (function)
asctime	converts a tm object to a textual representation (function)
strftime	converts a tm object to custom textual representation (function)
wcsftime	converts a tm object to custom wide string textual representation (function)
gmtime	converts time since epoch to calendar time expressed as Universal Coordinated Time (function)
localtime	converts time since epoch to calendar time expressed as local time (function)
mktime	converts calendar time to time since epoch (function)

Synopsis

#define NULL /* see definition */
#define CLOCKS_PER_SEC /* see definition */
#define TIME_UTC /* see definition */
namespace std {
  using size_t = /* see definition */;
  using clock_t = /* see definition */;
  using time_t = /* see definition */;
  struct timespec;
  struct tm;
  clock_t clock();
  double difftime(time_t time1, time_t time0);
  time_t mktime(struct tm* timeptr);
  time_t time(time_t* timer);
  int timespec_get(timespec* ts, int base);
  char* asctime(const struct tm* timeptr);
  char* ctime(const time_t* timer);
  struct tm* gmtime(const time_t* timer);
  struct tm* localtime(const time_t* timer);
  size_t strftime(char* s, size_t maxsize, const char* format, const struct tm* timeptr);
}

Class std::timespec

struct timespec {
  std::time_t tv_sec;
  long tv_nsec;
};

Class std::tm

struct tm {
  int tm_sec;
  int tm_min
  int tm_hour;
  int tm_mday;
  int tm_mon;
  int tm_year;
  int tm_wday;
  int tm_yday;
  int tm_isdst;
};