CODEWITHSUNDEEP
c++c++11c++14c++17
425nesp
425nesp

Reputation: 7593

Get the current date and time with milliseconds with only the standard library in C++

I'm trying to print a timestamp like this.

2018-05-24T20:16:07.339271

I don't want to use Boost or any third party libraries. I want to only use the standard library. I'm using Clang 6, so I should be able to use C++ 17 if necessary.

I started looking at chrono and have something like this.

auto now = std::chrono::high_resolution_clock::now();

But, I'm unsure how to get the datetime format that I want from above.

Upvotes: 4

Views: 1726

Answers (3)

CAF
CAF

Reputation: 1400

The following code uses standard C++ only. The data contained in *loc_time and milli_secs can be used to produce the desired output in local time. To get the output in UTC, use std::gmtime instead of std::localtime.

// get actual system time
const auto now = std::chrono::system_clock::now();

// get seconds since 1970/1/1 00:00:00 UTC
const auto sec_utc = std::chrono::system_clock::to_time_t(now);

// get pointer to tm struct (not thread safe!)
const auto loc_time = std::localtime(&sec_utc);

// get time_point from sec_utc (note: no milliseconds)
const auto now_s = std::chrono::system_clock::from_time_t(sec_utc);

// get milliseconds (difference between now and now_s
const auto milli_secs = std::chrono::duration<double, std::milli>(now - now_s).count() * .001;

Upvotes: 2

Jahangir
Jahangir

Reputation: 161

standard library c++ does not provide a proper date type, so you can use   
structs and functions from c which is inherited on c++. <ctime>  header
file need to include in c++ program. i think below code will help you.

    time_t now = time(0);
    cout<<now<<endl;
    tm *lt = localtime(&now);

Upvotes: -3

Andrei R.
Andrei R.

Reputation: 2462

guess your best bet is using std::localtime + std::put_time

Upvotes: 2

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