Hi all,
Got a wierd problem handling dates. I am retrieving a UTC timestamp
from a Postgresql (9.3.9) database, converting it to a date* and then
offsetting to a (variable) time zone.
eliding a lot of unrelated code:
:
(require (only-in srfi/19 date->string)
(except-in racket/date date->string))
:
(set! result (query-row db sql-cmd userid ))
:
(set! expires (vector-ref result 1))
(eprintf "=> expires ~s~n" expires)
(set! expires (sql-datetime->srfi-date expires))
(eprintf "=> expires ~s~n" expires)
:
(let* [
; convert UTC expire time to user's timezone
(expires (seconds->date (date*->seconds expires #f)
timezone))
:
]
(eprintf "=> expires ~s~n" expires)
:
with 'timezone' = -4 (EDT) this produces:
=> expires #(struct:sql-timestamp 2015 8 22 20 26 49585512000 0)
=> expires #(struct:date* 49 26 2022 8 2015 6 233 #f 0 585512000 "")
=> expires #(struct:date* 34 36 1622 8 2015 6 233 #t -14400 512000000
"Eastern Daylight Time")
The results are NOT repeatable ... e.g., another run produces:
=> expires #(struct:sql-timestamp 2015 8 22 20 57 40 483091000 0)
=> expires #(struct:date* 40 57 20 22 8 2015 6 233 #f 0 483091000 "")
=> expires #(struct:date* 43 5 17 22 8 2015 6 233 #t -14400 91000000
"Eastern Daylight Time")
and yet another run:
=> expires #(struct:sql-timestamp 2015 8 22 21 1 21 729173000 0)
=> expires #(struct:date* 21 1 21 22 8 2015 6 233 #f 0 729173000 "")
=> expires #(struct:date* 30 13 17 22 8 2015 6 233 #t -14400 173000000
"Eastern Daylight Time")
As you can see, it seems that *sql-timestamp->srfi-date* sometimes
botches the conversion, and it seems that (seconds->date
(date*->seconds)) sometimes is not symmetric. BIG BUT ... this ONLY
happens when the sql-timestamp comes from an actual database. This
simple test program :
(require
racket/date
db
db/util/datetime
)
(define db-time (sql-timestamp 2015 8 22 18 48 12 0 #f))
(define rkt-time (sql-datetime->srfi-date db-time))
(define timezone -4)
(define lcl-time (seconds->date (date*->seconds rkt-time #f) timezone))
(printf "DB : ~s~n" db-time )
(printf "RKT: ~s~n" rkt-time )
(printf "LCL: ~s~n" lcl-time )
correctly produces
DB : #(struct:sql-timestamp 2015 8 22 18 48 12 0 #f)
RKT: #(struct:date* 12 48 18 22 8 2015 6 233 #f 0 0 "")
LCL: #(struct:date* 12 48 14 22 8 2015 6 233 #t -14400 0 "Eastern
Daylight Time")
Can anyone shed light on what's happening? I really need these
copnverted timestamps to be correct.
Thanks,
George
--
You received this message because you are subscribed to the Google Groups "Racket
Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to racket-users+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
