nmeasim::core::time

namespace nmeasim::core::time · Library API

Date and time text handling, part of the nmeasim::core library.

It converts between ISO 8601 date-time text and std::chrono::system_clock time points in UTC, using only the calendar types of std::chrono, so the result never depends on the locale or the time zone of the host.

Summary

Functions

Name	Description
parse_iso8601()	Parses an ISO 8601 date-time into a UTC time point with millisecond precision.
format_iso8601()	Formats a UTC time point as YYYY-MM-DDThh:mm:ss.sssZ.

Functions

parse_iso8601()

std::optional<std::chrono::system_clock::time_point> parse_iso8601(std::string_view text)

Parses an ISO 8601 date-time into a UTC time point with millisecond precision.

Accepted, after leading and trailing whitespace is trimmed:

• a calendar date YYYY-MM-DD, which must exist (2024-02-29 does, 2026-02-30 does not);
• optionally a T or space separator and a time hh:mm, optionally followed by :ss and a fraction introduced by . or ,; digits beyond milliseconds are truncated. Hour 24 is accepted only as 24:00 or 24:00:00, with a fraction of zeros at most, meaning the end of the day, and second 60 for a leap second, which lands on the next minute;
• after a time, optionally Z or an offset +hh, +hhmm or +hh:mm (or with -), in hours up to 23 and minutes up to 59, which is subtracted to give UTC.

A date-time without an offset is taken as UTC, not local time. Basic-format dates without hyphens, week dates and ordinal dates are rejected.

Parameters

Name	Type	Description
text	std::string_view	Text to parse.

Returns std::optional<std::chrono::system_clock::time_point>: The instant in UTC, or std::nullopt when text is not a valid date-time of the accepted forms.

See also

• ISO 8601-1, extended format of calendar dates and times of day.

Declared in src/core/include/nmeasim/core/time/iso8601.hpp:41 · defined in src/core/src/time/iso8601.cpp:57

format_iso8601()

std::string format_iso8601(std::chrono::system_clock::time_point time_utc)

Formats a UTC time point as YYYY-MM-DDThh:mm:ss.sssZ.

The time is rounded down to whole milliseconds and the result always has three decimals, so a time point of whole milliseconds round-trips through parse_iso8601.

Parameters

Name	Type	Description
time_utc	std::chrono::system_clock::time_point	Instant to format; years outside 0000 to 9999 do not give valid ISO 8601 text.

Returns std::string: The date-time text, for example 2026-09-23T10:34:56.780Z.

Declared in src/core/include/nmeasim/core/time/iso8601.hpp:52 · defined in src/core/src/time/iso8601.cpp:180