text: #!/bin/bash
  
  [ -f testing.sh ] && . testing.sh
  
  #testing "name" "command" "result" "infile" "stdin"
  
  # Use a consistent TZ for these tests, but not GMT/UTC because that
  # makes mistakes harder to spot.
  tz=Europe/Berlin
  this_year=$(TZ=$tz date +%Y)
  
  # Use a consistent locale too.
  export LANG=C
  
  # Unix date parsing.
  testing "-d @0" "TZ=$tz date -d @0" "Thu Jan  1 01:00:00 CET 1970\n" "" ""
  testing "-d @0x123 invalid" "TZ=$tz date -d @0x123 2>/dev/null || echo expected error" "expected error\n" "" ""
  
  # POSIX format with 2- and 4-digit years.
  # All toyonly because coreutils rejects POSIX format dates supplied to -d.
  # These expected values are from running on the host without -d (not as root!).
  toyonly testing "-d MMDDhhmm" \
    "TZ=$tz date -d 06021234 +'%F %T'" "$this_year-06-02 12:34:00\n" "" ""
  toyonly testing "-d MMDDhhmmYY.SS" \
    "TZ=$tz date -d 1110143115.30" "Tue Nov 10 14:31:30 CET 2015\n" "" ""
  # busybox thinks this is the year 603 (ISO time 0602-12-34 19:82 with out of range fields normalized).
  toyonly testing "-d MMDDhhmmCCYY" \
    "TZ=$tz date -d 060212341982" "Wed Jun  2 12:34:00 CEST 1982\n" "" ""
  toyonly testing "-d MMDDhhmmCCYY.SS" \
    "TZ=$tz date -d 111014312015.30" "Tue Nov 10 14:31:30 CET 2015\n" "" ""
  
  # ISO date format.
  testing "-d 1980-01-02" "TZ=$tz date -d 1980-01-02" "Wed Jan  2 00:00:00 CET 1980\n" "" ""
  testing "-d 1980-01-02 12:34" "TZ=$tz date -d '1980-01-02 12:34'" "Wed Jan  2 12:34:00 CET 1980\n" "" ""
  testing "-d 1980-01-02 12:34:56" "TZ=$tz date -d '1980-01-02 12:34:56'" "Wed Jan  2 12:34:56 CET 1980\n" "" ""
  
  # Reject Unix times without a leading @.
  testing "Unix time missing @" "TZ=$tz date 1438053157 2>/dev/null || echo no" \
    "no\n" "" ""
  
  # Test just hour and minute (accepted by coreutils and busybox, presumably for setting the time).
  testing "-d 12:34" 'TZ=UTC date -d 12:34 | grep -q " 12:34:00 UTC $this_year" && echo OK' "OK\n" "" ""
  testing "-d 12:34:56" 'TZ=UTC date -d 12:34:56 | grep -q " 12:34:56 UTC $this_year" && echo OK' "OK\n" "" ""
  
  # Test the %N extension to srtftime(3) format strings.
  testing "%N" "touch -d 2012-01-23T12:34:56.123456789 f && date -r f +%Y%m%d-%H%M%S.%N" "20120123-123456.123456789\n" "" ""
  testing "%1N" "touch -d 2012-01-23T12:34:56.123456789 f && date -r f +%Y%m%d-%H%M%S.%1N" "20120123-123456.1\n" "" ""
  testing "%2N" "touch -d 2012-01-23T12:34:56.123456789 f && date -r f +%Y%m%d-%H%M%S.%2N" "20120123-123456.12\n" "" ""
  testing "%8N" "touch -d 2012-01-23T12:34:56.123456789 f && date -r f +%Y%m%d-%H%M%S.%8N" "20120123-123456.12345678\n" "" ""
  testing "%9N" "touch -d 2012-01-23T12:34:56.123456789 f && date -r f +%Y%m%d-%H%M%S.%9N" "20120123-123456.123456789\n" "" ""
  testing "%%N" "touch -d 2012-01-23T12:34:56.123456789 f && date -r f +%Y%m%d-%H%M%S.%%N" "20120123-123456.%N\n" "" ""
  testing "trailing %" "touch -d 2012-01-23T12:34:56.123456789 f && date -r f +%Y%m%d-%H%M%S.%" "20120123-123456.%\n" "" ""
  testing "just %" "touch -d 2012-01-23T12:34:56.123456789 f && date -r f +%" "%\n" "" ""
  rm -f f
  
  # Test embedded TZ to take a date in one time zone and display it in another.
  testing "TZ=" "TZ='America/Los_Angeles' date -d 'TZ=\"Europe/Berlin\" 2018-01-04 08:00'" "Wed Jan  3 23:00:00 PST 2018\n" "" ""
  testing "TZ=" "TZ='America/Los_Angeles' date -d 'TZ=\"Europe/Berlin\" 2018-10-04 08:00'" "Wed Oct  3 23:00:00 PDT 2018\n" "" ""
  testing "TZ= @" "TZ='America/Los_Angeles' date -d 'TZ=\"GMT\" @1533427200'" "Sat Aug  4 17:00:00 PDT 2018\n" "" ""
  
  # Test all supported UTC offset variants.
  testing "tz Z" \
    "date -u -d 2020-08-01T12:34:56Z" "Sat Aug  1 12:34:56 UTC 2020\n" "" ""
  testing "tz -0800" \
    "date -u -d 2020-08-01T12:34:56-0800" "Sat Aug  1 20:34:56 UTC 2020\n" "" ""
  testing "tz +0800" \
    "date -u -d 2020-08-01T12:34:56+0800" "Sat Aug  1 04:34:56 UTC 2020\n" "" ""
  testing "tz +08:00" \
    "date -u -d 2020-08-01T12:34:56+08:00" "Sat Aug  1 04:34:56 UTC 2020\n" "" ""
  testing "tz +8" \
    "date -u -d 2020-08-01T12:34:56+8" "Sat Aug  1 04:34:56 UTC 2020\n" "" ""
  testing "tz +08" \
    "date -u -d 2020-08-01T12:34:56+08" "Sat Aug  1 04:34:56 UTC 2020\n" "" ""
  testing "tz +008" \
    "date -u -d 2020-08-01T12:34:56+008" "Sat Aug  1 12:26:56 UTC 2020\n" "" ""
  
  # Can we parse date's own output format?
  testing "round trip" 'TZ=$tz date -d "$(TZ=$tz date -d @1598476818)"' \
    "Wed Aug 26 23:20:18 CEST 2020\n" "" ""
  