initial commit of Gregorian/IFC date conversion tools and unit tests

IFC.m

@@ -0,0 +1,53 @@
+function fixed = IFC(gregorian)
+arguments (Input)
+    gregorian (:,1) datetime
+end
+arguments (Output)
+    fixed (:, 4) table
+end
+% gregorian datetime 1 arg input?
+% y/m/d 3 args input?
+% TODO inputs validation
+
+% prepare output struct
+fixed = struct('Year', [], 'Month', '', 'Day', [], 'DayOfWeek', '');
+fixed = repmat(fixed, length(gregorian), 1);
+
+% eliminate time from input, only date matters
+gregorian.Hour = 0; gregorian.Minute = 0; gregorian.Second = 0;
+
+% year remains constant
+Year = num2cell(uint16(year(gregorian')));
+[fixed.Year] = Year{:};
+
+% find number of days into the current year
+Days = days(gregorian - datetime([fixed.Year] - 1, 12, 31)');
+
+% Calculate IFC month, number of days into that month, and if leap day
+% and/or year day occured
+[nMonths, nDays, leaped, yeared] = IFCmonths(Days, [fixed.Year]');
+
+% write month to output
+Month = num2cell(MONTHS(nMonths));
+[fixed.Month] = Month{:};
+
+% write number of days in month to output
+nDays = num2cell(nDays);
+[fixed.Day] = nDays{:};
+
+% write day of week to output
+DOW = num2cell(DAYSOFWEEK(mod([fixed.Day]', 7)));
+[fixed.DayOfWeek] = DOW{:};
+
+% Write year days as special days of the week
+yearDays = num2cell(repmat(DAYSOFWEEK(7), 1, sum(yeared)));
+[fixed(yeared).DayOfWeek] = yearDays{:}; % try 2 year/leap days in a vector input
+
+% Write leap days as special days of the week
+leapDayFlags = ~yeared & leaped & [fixed.Month]' == MONTHS(14) & [fixed.Day]' == 0; 
+leapDays = num2cell(repmat(DAYSOFWEEK(8), 1, sum(leapDayFlags)));
+[fixed(leapDayFlags).DayOfWeek] = leapDays{:};
+
+% convert output to table
+fixed = struct2table(fixed);
+end