The Sarum Calendar for 2019 has been added to Dr William Renwick’s Documents page. You can download it from there. It begins from 1st January, so if you need the current Advent, you need the final month of 2018. It is in English and follows the Gregorian calendar.
I warmly recommend the rest of this valuable site which is completing the resources we have for the Use of Sarum and its chant.
Dr Renwick’s site is sometimes inaccessible for technical reasons. If this is so, the text in question is as follows:
* * *
The Kalendar appearing here contains in the third column the information provided in the printed Sarum Kalendars such as that found at the front of the Breviarium 1531. In the fourth column appears the information found in the Pica which appear scattered throughout the Breviarium. Generally speaking the latter takes precedence over the former where they differ. This Kalendar is provided firstly as a guide to those who wish to follow the Sarum Liturgical Kalendar throughout the course of the year, and secondly for those who wish to gain an understanding of the nature of a typical Sarum or pre-Tridentine liturgical year. These Kalendars follow the Gregorian or Western calendar rather than the Julian calendar.