Years should be written using Anno Domini System?

This question is vague so I will answer as best as possible. Years may be written in any format in literature. You can choose to use the Anno Domini system or you can use the less religiously charged version BCE/CE (Before the Commone Era/ Common Era) In research papers, the standard form is BC or AD but BCE and CE are becoming more common. If you are referring to writing a piece you would use thecalendar system that works best for your material. For example, when writing about China you may want to use the Chinese calendar.