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Gmtime_s

As explained in Modern C

gmtime_s is an Annex K C library function that converts a time_t value to a broken-down UTC time in a caller-provided object.

Convert a timestamp to UTC

time_t stamp = time(NULL);\nstruct tm utc;\nstruct tm *result = gmtime_s(&stamp, &utc);\n\nThe caller supplies both the time_t value and the struct tm object that receives the broken-down UTC time.

gmtime_s is an Annex K C library function that converts a time_t value into broken-down universal time, UTC. Its result object is supplied by the caller. section 8.5

TAKEAWAY: Choose gmtime_s for UTC and localtime_s for local time; mktime performs the corresponding local-time conversion in the opposite direction. section 8.5

How Modern C covers it

How deep it goes
Defines the UTC distinction and interface signature but does not detail struct tm fields or conversion internals.
Examples
Uses a time_t value, a caller-declared struct tm object, and the gmtime_s declaration.
What it assumes
Uses time_t and struct tm without detailing their definitions or the individual broken-down fields.
What you can do after
Apply it via the C library to obtain broken-down UTC time in storage owned by the caller.
How it connects
Contrasts UTC conversion with localtime_s and relates the local-time inverse operation to mktime.
Cover of Modern C
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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Modern C. The section links point to the parts of the book it draws on.