gnucash master: A truly ancient bug, discovered with an Xcode-5.1 compiler warning.

[Bob Gustafson]

On 05/20/2014 07:20 PM, John Ralls wrote:
> On May 20, 2014, at 4:02 PM, Bob Gustafson <bobgus at rcn.com> wrote:
>> No, I am not doing it in GnuCash - but I wish I could.
>>
>> My comment is to encourage any effort in the direction of time and timezone support and discourage attempts to close off that path.
> I don’t think that that’s a direction we want to go. I can’t see many users making the effort to include the time they wrote a check, or swiped their debit card, or whatever. FWIW, one CC company seems to post everything at 1700. Every transaction looks like
>            <STMTTRN>
>              <TRNTYPE>DEBIT
>              <DTPOSTED>20140121170000.000
>
> Everybody else I use just reports posted dates.
>
>> As an example, here is a box of chocolates complete with timestamps..
>>
>> viewspread13.27.csv:12345678	09/23/2013		-40.32		EINZUG AUSLANDSLASTSCHRIFT|9208|CHF      49,50KURS1,2276000|KURS VOM 20.09.13    MAFD|ZUERICH-FL AM19.09.13 15.50|	LINDT ZRH CHXR          CHE| 10010000|	959566027|	EC-POSMAGNET6   GEB.EU 0,00|	002|	
> I see two dates and one timestamp. The timestamp may or may not be useful; there’s no way of knowing without detailed information from the bank about what it means. Here’s one guess: You made a purchase for CHF49.50 at 1550 on 19 Sept 2013 in Zurich. It was posted to the seller’s bank on 20 Sept and to your bank at $40.32 on the 23rd. That’s an effective exchange rate of $1.230/CHF.
> The rates, according to http://www.exchangerates.org.uk/CHF-USD-exchange-rate-history-full.html,
> were
>
> Monday 23 September 2013	1 CHF = 1.0979 USD
> Sunday 22 September 2013	1 CHF = 1.0984 USD
> Saturday 21 September 2013	1 CHF = 1.0987 USD
> Friday 20 September 2013	1 CHF = 1.0987 USD
> Thursday 19 September 2013	1 CHF = 1.0979 USD
>
> The actual rate used by the banks could have been any of those, or something else, but the spread is $.0008, or < 4¢ on the transaction out of the $4.25 the bank charged you. Talk about sweating the small stuff. I don’t see how you gain anything at all by knowing you made the purchase — or whatever actually happened — at 1550.
>
> Regards,
> John Ralls

Pretty good analysis!

The exchange was into Euros, so the historical exchange rate would have 
been:

Monday 23 September 2013	1 CHF = 0.8136 EUR  or 40.2732 EUR
Sunday 22 September 2013	1 CHF = 0.8120 EUR  or 40.1940
Saturday 21 September 2013	1 CHF = 0.8124 EUR  or 40.2138
Friday 20 September 2013	1 CHF = 0.8124 EUR  or 40.2138
Thursday 19 September 2013	1 CHF = 0.8115 EUR  or 40.1692

The actual euros deducted was -40.32 and the CHF spent was 49.50 or an exch rate of 0.8145

Picking the rate of 0.8124 gives a Euro deduction of 40.2138 - the actual deduction was 40.32, so whatever exchange rate the banks used, they did not lose money.

(The convenience of using a plastic card at the point of sale is certainly worth 10 euro cents!)

-------

All of this analysis and reporting can be done without human keystrokes, as long as the data is available. The fact that the transaction was done on a Thursday at 15:50 and not reported until the following Monday rather increases the time slop.

Suppose that the transaction was done at 12:50 and that was early enough to make an earlier bank forex time window and the deduction could then be reported on Friday 20 Sept (yes, unlikely..)

With enough transactions, some of these details of the forex mechanism could be teased out of an otherwise very boring bunch of numbers.

Bob G