Question

I convert two types of Strings to an ISO format using SimpleDateFormat for parsing and org.apache.commons.lang.time.DateFormatUtils for formatting (since they provide a ISO formatter out-of-the-box).

The pattern Strings for parsing are M/d/y H:m and d.M.y H:m. A typical String to convert may look either like 4/14/2009 11:22 or 4.14.2009 11:22. I initialize the parsers as follows:

SimpleDateFormat SLASH = new SimpleDateFormat(PATTERN_S, Locale.getDefault());
SimpleDateFormat DOT = new SimpleDateFormat(PATTERN_D, Locale.getDefault()); 

I get the the formatter:

  FastDateFormat isoFormatter = DateFormatUtils.ISO_DATETIME_TIME_ZONE_FORMAT

After creating a Date from the parsed String:

Date date = FORMAT_SLASH.parse(old);

it is formatted for output:

isoFormatter.format(date)

The strange thing is : when a String with slashes was converted, the output looks like 2009-04-14T11:42:00+01:00 (which is correct) but when a String with dots was converted, the output looks like 2010-02-14T11:42:00+02:00, shifting my timezone to somewhere between Finland and South Africa, the year to 2010 and the month to february

What is going wrong here and why?

EDIT : changed the output strings to match real output (damn you, cut-n-paste). The reason was the interchanged M and d in the pattern strings that I failed to notice. 14 seems to be a perfecty valid month – its next year’s february and even non-lenient settings can’t force the formatter to reject it. The timeshift issue is resolved and the reason for the TimeZone change is provided by Jim Garrison. Thanks Ahmad and Jim

Answer 1

Your dot pattern is d.M.y H:m while your example shows that you meant M.d.y H:m, I supposed this would throw a ParseException, but it doesn’t and it causes timezone issues.