Six departments split in 2012. The result is shown here.

Change history:

1. 1960: At independence, Chad was divided into prefectures which were further subdivided into sub-prefectures.
2. ~1973: The following changes are conjectural. They are the easiest way to explain the differences between the list of "districts" in Morris Fisher's first edition, 1967, and the map in "L'Évaluation des Effectifs de la Population des Pays Africains", 1982 (see Bibliography for both). Arada, Guéréda, and Iriba sub-prefectures split from Biltine; Bitkine and Mangalmé sub-prefectures split from Mongo; Gounou Gaya sub-prefecture formed, probably from parts of Fianga and Pala; Moundou sub-prefecture split into Beinamar and Benoyé; Ngouri sub-prefecture split from Bol; Abéché and Abéché Centre Urbain sub-prefectures merged to form Abéché; Fort-Archambault and Fort-Archambault-Urban sub-prefectures merged to form Sarh; name of Dnor sub-prefecture changed to Ouaddi-Rimé; name of Fort-Lamy-Rural sub-prefecture changed to N'Djamena-Rural; name of Fort-Lamy-Urban sub-prefecture changed to N'Djamena-Urban; name of Moundou Centre Urbain sub-prefecture changed to Moundou.
3. ~1986: Am Zoer sub-prefecture formed from parts of Biltine and Guéréda; Bébedjia and Goré sub-prefectures split from Doba; Béré sub-prefecture split from Kélo; Maro sub-prefecture split from Sarh; eastern part of Bousso sub-prefecture in Chari-Baguirmi prefecture transferred to Sarh sub-prefecture in Moyen-Chari prefecture; name of Nord-Kanem sub-prefecture changed to Nokou; name of Ouaddi-Rimé sub-prefecture changed to Djédaa. As a result, the sub-prefectures of Chad at the time of the 1993 census were as shown in this table.

1. 1999-06-10: Decree No. 226/PR/MISD/99 created many new administrative units. This is somewhat perplexing. The decree is quite straightforward in saying what units were created. All of them were sub-prefectures. The problem is that if you add these new sub-prefectures to the ones that existed before, there are some duplications and some omissions. The following description is extracted from the decree, but is known to be faulty.
2. Assinet, Fitri, and Koundjourou sub-prefectures created in Batha prefecture; Borkou Yala, Gouro, Kalait, Kouba, Ouadi-Hawar, Ounianga Kebbir, and Zouar sub-prefectures created in Borkou-Ennedi-Tibesti prefecture; Karal, Linia, Mandelia, Mani, and Moïto sub-prefectures created in Chari-Baguirmi prefecture; Michémiré and Salal sub-prefectures created in Kanem prefecture; Bagassola and Doum-Doum sub-prefectures created in Lac prefecture; Krim-Krim sub-prefecture created in Logone Occidental prefecture; Baïkoro, Béboto, and Bodo sub-prefectures created in Logone Oriental prefecture; Kim and Lagon sub-prefectures created in Mayo-Kébbi prefecture; Bohobé, Bouna, and Korbol sub-prefectures created in Moyen-Chari prefecture; Abdi, Adé, Chokoyan, and Koukou Angarana sub-prefectures created in Ouaddaï prefecture; Dono Manga sub-prefecture created in Tandjilé prefecture.
3. 1999-09-01: Decree No. 354/PR/MISD/99 created more administrative units. The same remarks apply as for the preceding decree.
4. Haraze Djombo Kibit sub-prefecture created in Batha prefecture; Mondo sub-prefecture created in Kanem prefecture; Liwa sub-prefecture created in Lac prefecture; Rigaza sub-prefecture created in Mayo-Kébbi prefecture; Hadjer Hadid and Mabrone sub-prefectures created in Ouaddaï prefecture; Dafra and Déressia sub-prefectures created in Tandjilé prefecture. As a result, Chad's 28 departments were subdivided into 108 sous-préfectures (sub-prefectures), and one commune (N'Djamena), which was divided into eight arrondissements. The table below shows the 108 sub-prefectures and N'Djamena.

1. 2002-10-17: Chad reorganized into 18 regions, subdivided into 47 departments and N'Djamena, as listed here.

1. 2008-02-19: Four new regions created: Borkou-Ennedi-Tibesti region split into Borkou, Ennedi, and Tibesti; Sila region split from Ouaddaï; and Barh el Ghazel region split from Kanem. Judging by comparison between the lists of departments, Abdi department split from Ouara; Abtouyour and Mangalmé departments split from Guéra; Barh el Gazel department split into Barh el Gazel Nord and Barh el Gazel Sud; Borkou Yala department split from Borkou; Ennedi Est department renamed Wadi Hawar, and its capital moved from Bahaï to Amdjarass; Ennedi Ouest department renamed Ennedi; Gueni department formed from parts of Dodjé and Ngourkosso; Kouh-Est, Kouh-Ouest, and La Nya departments split from Pendé (?); Mayo Lémié department split from Mayo Boneye; Mont Illi department split from Kabbia; Nord Kanem and Wadi Bissam departments split from Kanem; Tibesti department split into Tibesti Est and Tibesti Ouest.
2. 2012-09-04: Ennedi region split into Ennedi Est (the former Wadi Hawar department, former HASC code TD.EN.EE) and Ennedi Ouest (former Ennedi, TD.EN.EO). Am-Djarass department split from Wadi Hawar; Ennedi Ouest split into Fada and Mourtcha departments. In Bahr el Ghazel region, Barh el Gazel Ouest department split from Barh el Gazel Sud (TD.BG.BS). In Mayo-Kebbi Ouest region, Mayo Binder department split from Lac Léré (TD.MW.LL). In Tandjilé region, Tandjilé Centre department split from Tandjilé Ouest (TD.TA.TO). In Wadi Fira region, Kobé department (TD.BI.KO) split into Iriba and Mégri. I was unable to determine whether the new Iriba department covers the same territory as the Iriba department that existed from ~1973 to 2002. The resulting division into 67 departments and N'Djamena is as shown in the yellow table above.