While standard reference works give a date of ‘ca. 360 C.E.’ vel sim. for Codex Sinaiticus, this overly precise mid–fourth century date is more a matter of habit rather than the result of reasoned argumentation based on reliable evidence.

The Date of Codex Sinaiticus by Brent Nongbri (https://academic.oup.com/jts/advance-article/doi/10.1093/jts/flac083/6652265?searchresult=1&login=false)