| PARSEDATE(3) | Library Functions Manual | PARSEDATE(3) | 
parsedate —
#include <util.h>
time_t
  
  parsedate(const
    char *datestr, const
    time_t *time, const int
    *tzoff);
parsedate() function parses a datetime from
  datestr described in English relative to an optional
  time point, and an optional timezone offset (in minutes
  behind/west of UTC) specified in tzoff. If
  time is NULL then the current
  time is used. If tzoff is NULL,
  then the current time zone is used.
The datestr is a sequence of white-space separated items. The white-space is optional if the concatenated items are not ambiguous. An empty datestr is equivalent to midnight today (the beginning of this day).
The following words have the indicated numeric meanings:
    last = -1, this = 0,
    first, next, or
    one = 1, second is unused so
    that it is not confused with “seconds”, two
    = 2, third or three =
    3, fourth or four = 4,
    fifth or five = 5,
    sixth or six = 6,
    seventh or seven = 7,
    eighth or eight = 8,
    ninth or nine = 9,
    tenth or ten = 10,
    eleventh or eleven = 11,
    twelfth or twelve = 12.
The following words are recognized in English only:
    AM, PM,
    a.m., p.m.,
    midnight, mn,
    noon.
The months: january,
    february, march,
    april, may,
    june, july,
    august, september,
    october, november,
    december, and common abbreviations for them.
The days of the week: sunday,
    monday, tuesday,
    wednesday, thursday,
    friday, saturday, and common
    abbreviations for them.
Time units: year,
    month, fortnight,
    week, day,
    hour, minute,
    min, second,
    sec, tomorrow,
    yesterday.
Timezone names: gmt (+0000),
    ut (+0000), utc (+0000),
    wet (+0000), bst (+0100),
    wat (-0100), at (-0200),
    nft (-0330), nst (-0330),
    ndt (-0230), ast (-0400),
    adt (-0300), est (-0500),
    edt (-0400), cst (-0600),
    cdt (-0500), mst (-0700),
    mdt (-0600), pst (-0800),
    pdt (-0700), yst (-0900),
    ydt (-0800), hst (-1000),
    hdt (-0900), cat (-1000),
    ahst (-1000), nt (-1100),
    idlw (-1200), cet (+0100),
    met (+0100), mewt (+0100),
    mest (+0200), swt (+0100),
    sst (+0200), fwt (+0100),
    fst (+0200), eet (+0200),
    bt (+0300), it (+0330),
    zp4 (+0400), zp5 (+0500),
    ist (+0550), zp6 (+0600),
    ict (+0700), wast (+0800),
    wadt (+0900), awst (+0800),
    awdt (+0900), cct (+0800),
    sgt (+0800), hkt (+0800),
    jst (+0900), cast (+0930),
    cadt (+1030), acst (+0930),
    acst (+1030), east (+1000),
    eadt (+1100), aest (+1000),
    aedt (+1100), gst (+1000),
    nzt (+1200), nzst (+1200),
    nzdt (+1300), idle
  (+1200).
The timezone names specify an offset from Coordinated Universal Time (UTC) and do not imply validating the time/date to be reasonable in any zone that happens to use the abbreviation specified.
A variety of unambiguous dates are recognized:
Standard e-mail (RFC822, RFC2822, etc) formats and the output from date(1), and asctime(3) are all supported as input.
As well as times:
Relative items are also supported:
Note that, as a special case for midnight
    with the name of a day only, “midnight tuesday” implies 00:00
    at the beginning of Tuesday, whereas “Sat mn” implies 00:00 at
    the end of Saturday (i.e. early Sunday morning.)
Seconds since epoch, UTC, (also known as UNIX time) are also supported:
Text in datestr enclosed in parentheses
    ‘(’ and
    ‘)’ is treated as a comment, and
    ignored. Parentheses nest (the comment ends when there have been the same
    number of closing parentheses as there were opening parentheses.) There is
    no escape character in comments, ‘)’
    always ends (or decreases the nesting level of) the comment.
parsedate() returns the number of seconds passed since,
  or before (if negative,) the Epoch, or -1 if the date
  could not be parsed properly. A non-error result of -1
  can be distinguished from an error by setting errno to
  0 before calling parsedate(),
  and checking the value of errno afterwards.
NULL, then:
TZparsedate() was originally written by
  Steven M. Bellovin while at the University of North Carolina at Chapel Hill.
  It was later tweaked by a couple of people on Usenet. Completely overhauled by
  Rich $alz and Jim Berets in August, 1990.
The parsedate() function first appeared in
    NetBSD 4.0.
parsedate() function is not re-entrant or
      thread-safe.parsedate() function assumes years less than 0
      mean − year, and in non ISO formats, that
      years less than 70 mean 2000 + year, otherwise years
      less than 100 mean 1900 + year.parsedate() function accepts “12
      am” where “12 midnight” is correct, and similarly
      “12 pm” for “12 noon”. The correct forms are
      also accepted.| March 22, 2017 | NetBSD 9.3 |