ISLEAP Function

Calculate leap year

Description

ISLEAP returns 1 if Year is a leap year and 0 otherwise. ISLEAP is only set for gregorian calendar, so Year >= 1583.

The Gregorian calendar has 97 leap years every 400 years:
Every year divisible by 4 is a leap year.
However, every year divisible by 100 is not a leap year.
However, every year divisible by 400 is a leap year after all.
So, 1700, 1800, 1900, 2100, and 2200 are not leap years, but 1600, 2000, and 2400 are leap years.

You can find more details on:
http://www.advancedmcode.org/isleap.html

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• MATLAB release: MATLAB 6.5 (R13)

[Marc FC]

 

[Vince Petaccio]

Cool, just what I needed. Thanks! :o]

[Jan Simon]

CLOCK -> DATE -> DATESTR -> STR2DOUBLE waste a lot of time: str2double(datestr(date,10))
Faster: c = clock; default = {c(1)};

Checking the number of inputs can be done easier and faster without VARARGIN, e.g.:
  function x = isleap(Year)
  switch nargin
  case 1, % Your error checks...
  case 0, c = clock; Year = c(1);
  otherwise error(...);
  end

The permanent disabling of the warning for logical conversion is not secure. You can omit this by simplifying the engine - instead of:
  warning('OFF','MATLAB:conversionToLogical')
  A=logical(mod(Year,4));
  B=logical(mod(Year,100));
  C=logical(mod(Year,400));
  x=ismember(Year,Year(~C | (~A & B)));
call just:
  x = ~mod(Year, 4) & (mod(Year, 100) | ~mod(Year, 400));
And suddenly the function is 150 times faster (400 times if called without argument).
Good help, H1-line, date, author and reference included. I'll rate this, if its efficiency is encreased.

[Jan Simon]

Descriptive help, reliable error checking, new version is really efficient, does exactly what the name says.