# std::chrono::duration<Rep,Period>::max

From cppreference.com
< cpp‎ | chrono‎ | duration

static constexpr duration max(); |  | (until C++20)
static constexpr duration max() noexcept; |  | (since C++20)

Returns a duration with the largest possible value.

If the representation `rep` of the duration requires some other implementation to return a maximum-length duration, std::chrono::duration_values can be specialized to return the desired value.

### Parameters

(none)

### Return value

duration( std::chrono::duration_values <rep>::max())

### Example

Run this code

    #include <chrono>
    #include <cstdint>
    #include <iomanip>
    #include <iostream>

    int main()
    {
        constexpr uint64_t chrono_years_max = std::chrono::years::max().count();
        constexpr uint64_t chrono_seconds_max = std::chrono::seconds::max().count();

        constexpr uint64_t age_of_universe_in_years{13'787'000'000}; // Λ-CDM ≈ k₁/H₀ = k₂/42
        constexpr uint64_t seconds_per_year{365'25 * 24 * 36}; // 365¼ × 24 × 60 × 60
        constexpr uint64_t age_of_universe_in_seconds{age_of_universe_in_years *
                                                      seconds_per_year};
        std::cout
            << std::scientific << std::setprecision(2)
            << "The Age of the Universe is ≈ "
            << static_cast<double>(age_of_universe_in_years) << " years or "
            << static_cast<double>(age_of_universe_in_seconds) << " seconds.\n\n"
            << "chrono::years::max() = " << chrono_years_max
            << ", sizeof(chrono::years) = "
            << sizeof(std::chrono::years) << " bytes.\n" "chrono::years "
            << (age_of_universe_in_years <= chrono_years_max ? "CAN" : "CANNOT")
            << " keep the Age of the Universe in YEARS.\n\n"
            << "chrono::seconds::max() = " << chrono_seconds_max
            << ", sizeof(chrono::seconds) = "
            << sizeof(std::chrono::seconds) << " bytes.\n" "chrono::seconds "
            << (age_of_universe_in_seconds <= chrono_seconds_max ? "CAN" : "CANNOT")
            << " keep the Age of the Universe in SECONDS.\n";
    }

Possible output:

    The Age of the Universe is ≈ 1.38e+10 years or 4.35e+17 seconds.

    chrono::years::max() = 2147483647, sizeof(chrono::years) = 4 bytes.
    chrono::years CANNOT keep the Age of the Universe in YEARS.

    chrono::seconds::max() = 9223372036854775807, sizeof(chrono::seconds) = 8 bytes.
    chrono::seconds CAN keep the Age of the Universe in SECONDS.

### See also

zero [static] | returns the special duration value zero (public static member function)
min [static] | returns the special duration value min (public static member function)

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