# std::chrono::file_clock

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< cpp‎ | chrono

Defined in header `<chrono>` |  |
using file_clock = /* see below */; |  | (since C++20)

`std::chrono::file_clock` is an alias for the clock used for std::filesystem::file_time_type. Its epoch is unspecified.

`file_clock` meets the TrivialClock requirements.

### Time point family

Defined in namespace `std::chrono` |  |
template<class Duration> using file_time = std::chrono::time_point<std::chrono::file_clock, Duration>; |  | (since C++20)

operator<<(std::chrono::file_time) (C++20) | performs stream output on a file_time (function template)
from_stream(std::chrono::file_time) (C++20) | parses a file_time from a stream according to the provided format (function template)
std::formatter<std::chrono::file_time> (C++20) | formatting support for `file_time` (class template specialization)

### Member types

Member type | Definition
`rep` | signed arithmetic type representing the number of ticks in the clock's duration
`period` | a std::ratio type representing the tick period of the clock, in seconds
`duration` | std::chrono::duration<rep, period>, capable of representing negative durations
`time_point` | std::chrono::time_point<std::chrono::file_clock>

### Member constants

constexpr bool is_steady [static] | true if the time between ticks is always constant, i.e. calls to `now()` return values that increase monotonically even in case of some external clock adjustment, otherwise false (public static member constant)

### Member functions

`file_clock` provides exactly one of the following two pairs of static member functions:

- `to_utc` and `from_utc`; or
- `to_sys` and `from_sys`.

now [static] | returns a std::chrono::time_point representing the current point in time (public static member function)
to_utc from_utc [static] (optional) | converts between `file_time` and `utc_time` (public static member function)
to_sys from_sys [static] (optional) | converts between `file_time` and `sys_time` (public static member function)

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