The Julian Date Calculator spreadsheet below includes Ordinal Date calendars and worksheets for performing Ordinal Date conversions and Julian Date conversions using the methods listed above. Note that in order to display the day-fraction, you need to change the format of the cell to "General" or "Number". The second formula works because Excel stores time values as a fraction of a day so that (noon=0.5). Where xltime refers to a cell containing a time value. To include the TIME in the Julian Date conversion, you can use a couple of different formulas to add in the day-fraction for a time specified as HH:MM:SS (24-hour Greenwich Mean Time): =( HH+( MM+ SS/60)/60)/24 or simply = xltime Keep in mind that the Gregorian calendar starts on 1. Using the formula from, the Julian Date for any date in the Gregorian calendar (at 0:00 GMT) can be calculated using: =367* Y - INT(7*( Y + INT(( M+9)/12))/4) The problem is that this only works for years after 1901. Where Y is the year, M is the month, and D is the day, and DATE( Y, M, D) could be replaced with just a standard Excel date. The Excel help documentation suggests using the following conversion to calculate a Julian Date: = DATE( Y, M, D)+2415018.5 Also, standard Excel dates correspond to the Gregorian Calendar (established in 1582). Note that UT (Universal Time) is typically known as GMT (Greenwich Mean Time). A better way in my opinion is converting from the format "yyyyddd" which avoids having to use the century variable, and datetext can be numeric: = DATE( INT( datetext/1000),1, MOD( datetext,1000)) Julian Date (Julian Day Number) Conversionsįor Julian Dates calculated as the number of days since Noon (UT), BC and datetext is the date in the format "yyddd". This can be done using the following date conversion formula: = DATE( century+ INT( datetext/1000),1, MOD( datetext,1000)) Note that standard Excel dates ( xldate) are only defined between and December 31, 9999, so formulas that use Excel's built-in date functions will likely only work in this range.Ĭonvert a date in the form "yyddd" to a Standard Date. When using the format "yyyyddd", you can replace "yy" with "yyyy" in the above formula, or because there are no leading zeros, you don't have have to treat the Ordinal date as text, leading to the following formula: = YEAR( xldate)*1000+ xldate- DATE( YEAR( xldate),1,0) (Due to Y2K, this isn't a very safe format. Convert a standard Excel date to the date format "yyddd".
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