This article attempts to establish the precise date of the foundation of the Cistcian nunnery at Ołobok. So far historians have pointed to either 1211 or 1213. The divergence is the consequence of the loss of Władysław Odonic's original grant know it only from a copy o f a transumpt compiled for by Duke Przemysł II on 28 December 1292, copied with other privileges conferred on that monastery by Kin Władyław Łokietek on 1 January 1329. In transumpt of Przemysł, after the record of Odonic's grant, there are two grants, one forged, made in the name of Wierzbięta Klemensic, and the other authentic and dated (20 October 1213) signed by Archbishop Henryk Kietlicz. This inquiry into the beginnings of the nunnery at Ołobok also makes use of some later Cistercian sources, eg. Liber mortuorum from the Paradyż monastery, Adam of Szadek's chronicle of the Byszewo monastery and two Cistercian inventories from the MS of the deputy prior of Wągrowo Łukasz of Borek They, too, assign two different dates to the foundation of the Ołobok monastery, November 1211 (Zygmunt Strychowski's inventory; other 17th century Cistercian inventories merely mention the year date 1211) and 20 October 1213 (the date of Archbishop Kietlicz's endowment). The simplest way of accounting for this inconsistent reference in the written records is to surmise that Zygmunt Strychowski must have made a mistake while copying the text of the original foundation charter. It is entirely plausible that anno Domini 1211 Calendas Novembris in the inventory was derived from the date Anno Domini 1311 Kalendas Novembris, as it must have been entered in the original. That date notation translates into 22 X (October) 1213, ie. the exact date of the consecration of the Ołobok church as recorded by transumpt of Przemysł II. We may therefore suggest the following sequence of events. The foundation charter of the Ołobok monastery may have taken a few days to write in October 1213; was probably ready by 22 X 1213, ie. two days after the consecration of the Ołobok church, marked by Archbishop Kietlicz's grant. In later Cistercian inventories that date appears distorted, as 1 XI 1211. The date of the consecration of the Ołobok church (20 October 1213) must have been the only date left in Władysław Odonic's original document; it was then copied and passed on by the transumpt of Przemysł II.