Question

I’ve noticed an issue with some data I’m processing (2000+ lines of data).

The problem is very strange: the code works fine! UNTIL a specific date is reached (in this case 01/08/2011) when JavaScript fails to generate the correct date?

So, to explain: I’m taking a string in the format of ‘dd/mm/yyyy’ and doing (which doesn’t work):

• var date = '01/08/2011'.split('/');
• var milliseconds = new Date(date[2], parseInt(date[1]) - 1, date[0]).getTime(); => 1291161600000
• new Date(1291161600000); => Wed Dec 01 2010 00:00:00 GMT+0000 (GMT)

…but yet that exact code works fine with any date before the 1st August 2011?

So try again with 29/07/2011…

• var date = '29/07/2011'.split('/');
• var milliseconds = new Date(date[2], parseInt(date[1]) - 1, date[0]).getTime(); => 1311894000000
• new Date(1311894000000); => Fri Jul 29 2011 00:00:00 GMT+0100 (BST)

The only difference is the (GMT) and (BST) values returned, which suggests a locale issue. But why would that occur, and how can I fix the code to work around that?

Many thanks for any help you can give me.

Answer 1

You are doing octal!

Use a radix!

parseInt(date[1],10)

From the MDN Docs parseInt(string[, radix]):

If radix is undefined or 0, JavaScript assumes the following:

• If the input string begins with “0x” or “0X”, radix is 16 (hexadecimal).
• If the input string begins with “0”, radix is eight (octal). This feature is non-standard, and some implementations deliberately do not
  support it (instead using the radix 10). For this reason always
  specify a radix when using parseInt.
• If the input string begins with any other value, the radix is 10 (decimal).