LEADING FEATURES OF THE GREGORIAN REFORM The Gregorian Reform is an ingenious and, indeed, brilliant practical solution of the problems presented by the condition of the Kalendar at the close of the sixteenth century. The characteristic features of the Gregorian system will now be described. 1. It was known that the true vernal equinox was at this date (1582) about ten days earlier than March 21 as marked in the Kalendar. Should the equinox be fixed as at March 11? It was resolved to keep the equinox at the nominal date of March 21, and to bring the date into conformity with facts by the simple process of striking out ten nominal days. It was decreed that the day following Oct. 4, 1582 (when what is known as the New Style was to make its beginning), should be counted, not as Oct. 5, but as Oct. 15. And thus in the following year, 1583, the true vernal equinox would fall on March 21, as it was supposed to have fallen in A.D. 325, the date of the Council of Nicaea. 2. But how was it to be provided that in the future the same errors which had vitiated the old Kalendar should not come in time to vitiate the new? It will be remembered that the time of the old Kalendar had gained on true solar time at the rate, almost precisely, of one day in every 130 years. If the counting of one day could be suppressed in every 130 years, the end would be obtained. For purposes of practical convenience the reformers of the Kalendar assumed that 133 years should be taken as the period in which the Kalendar time exceeded the solar time by one day. The difference, for the purpose in hand, was insignificant; and, as will be seen hereafter, this deliberately chosen error will not affect the Kalendar to the extent of one day till A.D. 5200, while it makes calculations much simpler. Now the plan adopted to prevent the accumulation of the error in the old Kalendar was as follows: if one day could be withdrawn in every 133 years, or, what is the same thing, three days in every 399 years, the object would be attained.