"The release change of the IS retail-system from 4.0B to 4.6 and that of further systems in the SAP environment (catalog system, CRM, shop solution etc,) was carried out on time and without any start-up problems. ... After the changeover weekend ..."
http://www.fis-uk.eu/?l=&modul=news&site=news_overview&&ms=9...

"The tests also presented the opportunity to assess the planning of the changeover weekends. In particular, a fully-fledged “rehearsal” of the first changeover weekend took place with all NCBs on 29 and 30 September 2007. "
http://www.ecb.int/pub/pdf/annrep/ar2007en.pdf

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Note added at 25 mins (2010-10-13 07:30:04 GMT)
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this is talking about the arrival of the Euro :

"At the final stage of the cash changeover, a so-called cockpit was installed in each central bank, where a small number of high-ranking experts supervised the cash changeover weekend and, just in case, stood ready to take urgent measures or decisions."
http://www.oenb.at/de/img/feei_05__1_tcm14-29785.pdf