CHINESE LANGUAGE RESOURCES

兩千年中西曆轉換, a software for converting historical Chinese dates from the Han through Republican periods to Christian Gregorian (modern Western) dates, and vice versa:

https://sinocal.sinica.edu.tw

中华古籍资源库 has a database of historical texts:

http://read.nlc.cn/allSearch/searchList?searchType=25&showType=1&pageNo=1

古籍與特藏文獻資源 has a database of historical texts:

https://rbook.ncl.edu.tw/NCLSearch/

Kanseki Repository has a database of historical texts:

https://www.kanripo.org/catalog?coll=KR2

National Palace Museum Digital Library of Qing Archives:

https://qingarchives.npm.edu.tw/index.php

The First Historical Archives of China's website has full text of certain Qing imperial court materials such as《清實錄》 and《清會典》：

https://fhac.com.cn/fulltext_detail/2/348529