1601 (MDCI) was a common yearstarting on Monday of the Gregorian calendar and a common year starting on Thursday (dominical letter D) of the Julian calendar, the 1601st year of the Common Era (CE) and Anno Domini (AD) designations, the 601st year of the 2nd millennium, the 1st year of the 17th century, and the 2nd year of the 1600s decade. As of the start of 1601, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923. January 1 of this year (1601-01-01) is used as the base of file dates and of Active Directory Logon dates by Microsoft Windows. It is also the date from which ANSI dates are counted and were adopted by the American National Standards Institute for use with COBOL and other computer languages. This epoch is the beginning of the 400-year Gregorian leap-year cycle within which digital files first existed; the last year of any such cycle is the only leap year whose year number is divisible by 100. All versions of the Microsoft Windows operating system from Windows 95 onward count units of one hundred nanoseconds from this epoch.
^Palmer, Alan; Veronica (1992). The Chronology of British History. London: Century Ltd. pp. 166–168. ISBN0-7126-5616-2.
^Edwards, Phillip, ed. (1985). Hamlet, Prince of Denmark. New Cambridge Shakespeare. Cambridge University Press. p. 8. ISBN0-521-29366-9. Any dating of Hamlet must be tentative. Scholars date its writing as between 1599 and 1601.