Besides the famous getYear ECMAScript date parsing is so badly specified that it is full of quirks. Opera has a good share of them..
Some random testing in IE7, Firefox 2 and Opera 9 shows that a simple new Date(somestring) dishes up several surprises:
- Opera seems to be the only one that tries to parse European date formats, though it defaults to U.S. format for ambiguous dates. Hence, "1/2/2008" is January 2nd while "30/10/2008" is October 30th in Opera.
- Greater than expected values for a specific part increases the whole date value in IE and Firefox. In other words, passing in January 32nd returns February first.
- ..but this is more thoroughly implemented in Firefox than IE, "1/1/2008 23:59:60" gives you January 2nd in the former and NaN in the latter.
- Opera defaults to values from current timestamp on computer for any input that doesn't make sense. In other words, if you pass in January 32nd on April 11th, January 11th is not-quite-expected outcome..
- The IE and Firefox parsers support both m-d-y and y-m-d formats. So if the input is ambiguous, how do they know which is which? Elementary, dear Watson: if the first integer is greater than 70 it is assumed to be a year. If it is less than 70 it is assumed to be a month. "69-1-1" is obviously a 1906 date while "70-1-1" is new year's day 1970. Ah, the magic of arbitrary heuristics.
- Speaking of the magic number "70", why can Firefox parse "1 january 70" but says "invalid date" for "1 january 69"??
- ..and why does Opera refuse to recognise single digits as valid years, just substituting the current year instead? Opera, pretending "1 january 9" is today's date is NOT the correct fix for those Y2K bugs.. 😥
- Finally, a quirk I'll leave my readers to ponder the inner workings of: if I tell Opera to parse "january 100 2007" on this very day, April 11th 2007 I get "Thu, 11 Jan 2007", which is consistent with the observation that it replaces out-of-range values with current values. Now, who can explain what Opera does if you parse "january 101 2007"?
Executive summary: good thing we're writing browsers and not time machines!