On 11/06/2016 09:42 PM, George Neuner wrote:
[...]
The following in Racket gets it wrong.
e.g.,
[...]
=>
#(struct:sql-timestamp 2016 5 1 5 0 0 0 0) -> "2016-05-01 05:00:00Z"
"2016-05-01 00:00:00-05" -> #(struct:sql-timestamp 2016 5 1 0 0 0 0
-18000)
#(struct:sql-timestamp 2016 6 12 5 0 0 0 0) -> "2016-06-12 05:00:00Z"
"2016-06-12 00:00:00-05" -> #(struct:sql-timestamp 2016 6 12 0 0 0 0
-18000)
I've converted the output in both directions to show the difference.
As you can see, the date returned as text is correct, but the date
returned as a sql-timestamp value is wrong.
I believe the db library is correct: "2016-05-01 05:00:00Z" and
"2016-05-01 00:00:00-05" refer to the same point in time.
> (require srfi/19)
> (define (string->utc x)
(date->time-utc (string->date x "~Y~m~d ~H~M~S~z")))
> (string->utc "2016-05-01 05:00:00Z")
(tm:time 'time-utc 0 1462078800)
> (string->utc "2016-05-01 00:00:00-05")
(tm:time 'time-utc 0 1462078800)
Similarly, the two sql-timestamp values refer to the same point in time
as above:
> (define (sql->utc x) (date->time-utc (sql-datetime->srfi-date x)))
> (sql->utc (sql-timestamp 2016 5 1 5 0 0 0 0))
(tm:time 'time-utc 0 1462078800)
> (sql->utc (sql-timestamp 2016 5 1 0 0 0 0 -18000))
(tm:time 'time-utc 0 1462078800)
See also the notes on PostgreSQL timestamptz here:
http://docs.racket-lang.org/db/notes.html#%28part._postgresql-timestamp-tz%29
Ryan
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