Chang'an (779) — the same event in Old Book of Tang, New Book of Tang and Zizhi Tongjian

Old Book of Tang: Daizong died in the inner hall of Zichen Hall and left an edict for the crown prince to ascend before the bier.; New Book of Tang…

What each source says

Old Book of Tang (Jiu Tangshu), Annals · AD 779 · 長安

Daizong died in the inner hall of Zichen Hall and left an edict for the crown prince to ascend before the bier.

是夕,上崩於紫宸之內殿。
Location: 舊唐書 卷11 大歷14年 5月

New Book of Tang (Xin Tangshu), Annals · AD 779 · 長安

Emperor Daizong died in the Zichen Inner Hall.

皇帝崩于紫宸內殿,年五十三
Location: 新唐書 卷006 肅宗·代宗 大曆14年5月

Zizhi Tongjian (Comprehensive Mirror) · AD 779 · 長安

In May 779, that night the emperor (Daizong) dies in the Zixin inner palace, and by testamentary edict Guo Ziyi concurrently holds the post of Grand Councilor.

是夕,上崩於紫宸之內殿,遺詔以郭子儀攝塚宰。
Location: 권225 779년 항

Place: 長安

Show on the map — open Old Book of Tang (Jiu Tangshu), Annals