From 1483434d2ca90be92477425fca49fb55bdf5e8f6 Mon Sep 17 00:00:00 2001 From: rubidium Date: Mon, 1 Jan 2007 22:00:54 +0000 Subject: (svn r7731) -Fix (r5999): off-by-one error in the date to YMD calculation for first 4 years of a century that was not divisable by 400. --- date.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/date.c b/date.c index 631e88ba3..66bade3c9 100644 --- a/date.c +++ b/date.c @@ -92,9 +92,22 @@ void ConvertDateToYMD(Date date, YearMonthDay *ymd) int rem = date % (365 * 400 + 97); uint16 x; - /* There are 24 leap years in 100 years */ - yr += 100 * (rem / (365 * 100 + 24)); - rem = rem % (365 * 100 + 24); + if (rem >= 365 * 100 + 25) { + /* There are 25 leap years in the first 100 years after + * every 400th year, as every 400th year is a leap year */ + yr += 100; + rem -= 365 * 100 + 25; + + /* There are 24 leap years in the next couple of 100 years */ + yr += 100 * (rem / (365 * 100 + 24)); + rem = (rem % (365 * 100 + 24)); + } + + if (!IsLeapYear(yr) && rem >= 365 * 4) { + /* The first 4 year of the century are not always a leap year */ + yr += 4; + rem -= 365 * 4; + } /* There is 1 leap year every 4 years */ yr += 4 * (rem / (365 * 4 + 1)); -- cgit v1.2.3-70-g09d2