Date conversion using GMT

I have a specific application in which I am reading in data into an array that includes a year (as an individual cell) and a GMT day. I need to convert the GMT day into an actual date using the year. If the year is in variable yr and GMT date in dGMT, I assumed that I could use the datestr function as follows:

d = datestr(addtodate(dGMT),floor(yr*365.25),'day'))

where datestr of the GMT returned the date in year 0000, and I simply add the amount of days that have elapsed since 1/1/0000. However, the data that is computed is off by about 2 weeks.

I did some investigating, and tried the above line of code with various years and dGMT=1.

I got the following: K>> datestr(addtodate((1),floor(1582*365.25),'day'))

ans =

31-Dec-1581

K>> datestr(addtodate((1),floor(1583*365.25),'day'))

ans =

10-Jan-1583

It seems that between year 1582 and 1583 10 days get added. Can anyone explain why, or possibly suggest another way to get the date?

Answer 1

[Walter Roberson]

There is actually good reason; see http://en.wikipedia.org/wiki/Gregorian_calendar