os/strftime

    cfunction
    src/core/os.c on line 1970, column 1

    (os/strftime fmt &opt time local)

    Format the given time as a string, or the current time if `time` is 
    not given. The time is formatted according to the same rules as the 
    ISO C89 function `strftime()`. The time is formatted in UTC unless 
    `local` is truthy, in which case the date is formatted for the 
    local timezone. The local timezone can be set by setting the `TZ` 
    environment variable. See `tzset()` (`<time.h>`) or 
    `_tzset()`(`<time.h>`) for further details.