Tbeli Abuserisdze (c. 1190 – 1240) was a medieval Georgian

Georgia (country)

Georgia is a sovereign state in the Caucasus region of Eurasia. Located at the crossroads of Western Asia and Eastern Europe, it is bounded to the west by the Black Sea, to the north by Russia, to the southwest by Turkey, to the south by Armenia, and to the southeast by Azerbaijan. The capital of...

 scholar and religious writer. A son of Ivane Abuserisdze

Abuserisdze

The Abuserisdze were a noble family in medieval Georgia. The first known members of the family, Ioane and his son, Abuser, served loyally to King Bagrat IV as hereditary holders of Artanuji and Khikhata . Abuser was also a commandant of Atskuri and Tsikhisjvari and the governor of the Armenian...

, eristavt-eristavi

Eristavi

Eristavi was a Georgian feudal office, roughly equivalent to the Byzantine strategos and normally translated into English as "duke". In the Georgian aristocratic hierarchy, it was the title of the third rank of prince and governor of a large province...

("archduke") of Khikhata

Khikhata

- References :...

 (Upper Adjara

Adjara

Adjara , officially the Autonomous Republic of Adjara , is an autonomous republic of Georgia.Adjara is located in the southwestern corner of Georgia, bordered by Turkey to the south and the eastern end of the Black Sea...

, southwestern Georgia), he is principally known for his original treatise, The Complete Timekeeper, which contains information related to calendar

Calendar

A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...

s, descriptions of different systems for maintaining chronology

Chronology

Chronology is the science of arranging events in their order of occurrence in time, such as the use of a timeline or sequence of events. It is also "the determination of the actual temporal sequence of past events".Chronology is part of periodization...

, dates of ecclesiastic holidays, tables of moonrise and moonset, information on special cycles, etc. Abuserisdze's work is purely theoretical, based largely upon his own mathematical investigations rather than on direct astronomical observations. Beyond this treatise, he authored The Miracles of Saint George

Saint George

Saint George was, according to tradition, a Roman soldier from Syria Palaestina and a priest in the Guard of Diocletian, who is venerated as a Christian martyr. In hagiography Saint George is one of the most venerated saints in the Catholic , Anglican, Eastern Orthodox, and the Oriental Orthodox...

... and the Testament of the Author, a work of religious as well as of historical character, in which he relates, among other things, the history of the Abuserisdze family. He has been canonized by the Georgian Orthodox Church.